- Email: [email protected]
The history of the earth's crust
438
BOOK REVIEWS
r e q u i r e d for t h e i r p r o d u c t i o n , a n d t h e n s a y s : " S u c h p r e s s u r e s axe t o o s m a l l t o b e c o n s i s t e n t with the parent-body radii...". Parent bodies in t h e 100 k m r a n g e of r a d i i as c o n s i d e r e d i n t h e discussion w o u l d h a v e c e n t r a l p r e s s u r e s o f t h e o r d e r o f 0.5 kilobaxs a n d , t h u s , t h e a b o v e m e n t i o n e d p r e s s u r e s are t o o large, n o t " t o o s m a l l " for t h e s e bodies, a m i s l e a d i n g a n d r a t h e r p u z z l i n g lapsus linguae. H e also does n o t i n d i c a t e t h e b a s i s for t h e e s t i m a t e s o f r a d i i of t h e p a r e n t bodies which depend on hypothetical heating and cooling t i m e s a n d are of n o a v a i l i f t h e b r e a k u p in collisions h a p p e n e d a t a n e a r l y e p o c h o f t h e prep l a n e t a r y stage. Collison t i m e s , n o t h e a t i n g or cooling times, w o u l d b e decisive. T h e d i a m o n d s , as well as t h e W i d m a n s t / i t t e n p a t t e r n , c o u l d t h e n b e easily reconciled w i t h s u b l u n a r size b o d i e s of a b o u t 1000 k m radius, m o d e r a t e l y h e a t e d i n r a p i d a c c r e t i o n a n d b r o k e n u p soon a f t e r f o r m a tion, w i t h c e n t r a l p r e s s u r e s a n d t e m p e r a t u r e s o f t h e o r d e r of 50 k b a n d 600°K, r e s p e c t i v e l y . T h e proposed production of diamonds in Canyon D i a b l o b y m e r e s h o c k a t i m p a c t looks like a m e c h a n i c a l i m p o s s i b i l i t y - - t h e t i m e is t o o s h o r t , a n d t h e r e q u i r e d h i g h p r e s s u r e s w o u l d h a v e led t o complete destruction of the specimens. The Canyon Diablo meteorites can only be fragments f r o m t h e r e a r o f t h e m a i n b o d y w h i c h were t h u s p r e s e r v e d f r o m t h e a p p l i c a t i o n of t o o h i g h pressures. I n his c o s m o g o n y t h e a u t h o r also cites t h e ' H a y a s h i c o n t r a c t i v e p h a s e " of s t a r f o r m a t i o n ' as s o m e t h i n g s e l f - e v i d e n t a n d b e l o n g i n g to t h e h a r d w a r e of a s t r o p h y s i c s . Y e t t h i s p h a s e , following u p t h e collapse of a g r a v i t a t i o n a l i n s t a b i l i t y i n a gaseous m e d i u m , p r o b a b l y n e v e r d i d t a k e place in t h e solar s y s t e m . E v e n a t as low a t e m p e r a t u r e as 4°K, f o r m a t i o n of a solar m a s s t h r o u g h s p o n t a n e o u s c o n t r a c t i o n of t h e i n s t a bilities w o u l d r e q u i r e a n i n i t i a l d e n s i t y i n t h e p a r e n t n e b u l a of a b o u t 2.5 × 10 -21 g m / c m 3, 1000 t i m e s h i g h e r t h a n in t h e i n t e r s t e l l a r m e d i u m . A t 100°K, t h e d e n s i t y w o u l d e x c e e d 4 x 10-17gin/ c m 3. N o w h e r e i n t h e spiral a r m s , or i n t h e cosmic clouds (where s t a r s are seen t o o r i g i n a t e curr e n t l y ) c o u l d s u c h c o n d e n s a t i o n s t a k e place, exc e p t t h r o u g h p r e l i m i n a r y f o r m a t i o n of nuclei f r o m t h e solid c o n t e n t s of space, w h i c h t h e n w o u l d g r o w b y a c c r e t i o n , n u t collapse. T h e article o n p u l s a r s b y T h o r n e is clear a n d b r o u g h t to t h e level o f g r a d u a t e s t u d e n t s , despite s u c h i n v o l v e d s u b j e c t s as g e n e r a l r e l a t i v i t y effects a n d g r a v i t a t i o n a l r a d i a t i o n . I t is easier t o s h o w w h a t t h e p u l s a r s are n o t t h a n w h a t t h e y a r e ; n e v e r t h e l e s s , in t h e case of t w o p u l s a r s w i t h a s t a b l e p e r i o d a r o u n d 1 sec a n d a less s t a b l e one of a b o u t 0.01 sec, a good w o r k i n g h y p o t h e s i s is t h a t of a n e u t r o n s t a r r o t a t i n g w i t h a p e r i o d of 1 sec a n d s i m u l t a n e o u s l y p u l s a t i n g in 0.01 sec. I t s
m a s s w o u l d b e 0.1-0.2 solar masses, t h e r a d i u s 50 t o 200 k m , t h e c e n t r a l d e n s i t y 3 × 1013 t o 1014 g m / e m s, b e i n g h i g h l y c e n t r a l l y c o n d e n s e d w i t h a large diffuse e n v e l o p e . I n M o t i o n s i n t h e A t m o s p h e r e of J u p i t e r , b y R . M. Goody, t h e r e is t o o m u c h u n e x p l a i n e d j a r g o n t o b e followed u p b y a n a v e r a g e g r a d u a t e s t u d e n t of a s t r o p h y s i c s . " A c c e l e r a t i o n " is h e r e u s e d i n t h e sense o f difference i n t h e a n g u l a r velocity of rotation, and not in its ordinary s e n s e - - a t r i v i a l t h i n g for p l a n e t a r y observers, b u t n o t for novices. A n d w h a t is " T h e Coriolis parameter" ?--there could be several of them. T h e w e l l - w r i t t e n article b y B u r b i d g e o n t h e g a l a c t i c m a g n e t i c field, d e s p i t e all t h e u n c e r t a i n ires of i n t e r p r e t a t i o n , l e a v e s one w i t h t h e imp r e s s i o n t h a t t h e g e n e r a l field is m u c h w e a k e r t h a n f o r m e r l y s u p p o s e d , p e r h a p s o n l y of t h e o r d e r of 10 -6 gauss, b u t t h a t t h e g a l a c t i c r a d i o e m i s s i o n w h i c h r e q u i r e d a s t r o n g e r field "is m a d e u p largely of r a d i a t i o n f r o m d i s c r e t e s o u r c e s . " T h e article b y Dessler o n t h e solar w i n d is also clear e n o u g h t o b e u n d e r s t o o d b y t h e n o n i n i t i a t e d . I n a d v o c a t i n g t h e h y d r o d y n a m i c flow s o l u t i o n for t h e solar w i n d , he, h o w e v e r , fails t o s h o w t h e source o f e n e r g y i n t h e e x p a n s i o n . U n l e s s t h e i n i t i a l t e m p e r a t u r e is i t s e l f sufficient a n d of t h e o r d e r of 2 × 107 °K, t e n t i m e s h i g h e r than the coronal temperature, conductivity of the hot plasma must be advocated to heat up the gas c u r r e n t l y . I f t h i s were n o t so, t h e a b i l i t y of t h e hydrodynamic stream to escape the gravitational field o f t h e S u n w o u l d look like a k i n d ofperpe-
tuum mobile. T h e m e r e f a c t t h a t t h i s first issue of t h e n e w " C r i t i c a l J o u r n a l " h a s p r o v o k e d h e r e n e w chall e n g i n g c o m m e n t s or e v e n d i s s e n t m a y b e reg a r d e d as a n i n d i c a t i o n t h a t i t h a s s e r v e d its p u r p o s e well in s t i m u l a t i n g critical t h o u g h t .
E. J. 0PIK
Dept. of Physics and Astronomy University of Maryland, College Park, Maryland and Armagh Observatory, Northern Ireland The History of the Earth's Crust. Edited by R . A. P H I ~ . Y . P r i n c e t o n U n i v e r s i t y Press, P r i n c e t o n , N e w J e r s e y , 1968. 244 pp. P r i c e $13.50. This book includes papers presented at a s y m p o s i u m o n T h e H i s t o r y o f t h e E a r t h ' s Crust h e l d a t t h e G o d d a r d I n s t i t u t e for Space S t u d i e s i n N o v e m b e r , 1966. U n f o r t u n a t e l y i t h a s required t w o y e a r s t o p u b l i s h t h e s e p r o c e e d i n g s ; in a r a p i d l y d e v e l o p i n g field t h i s seriously det r a c t s f r o m t h e v a l u e of a p u b l i c a t i o n . B a s i c a l l y
BOOK REVIEWS the contents of the book present the evidence supporting continental drift and sea floor spreading. I9o discussion is included of either ocean trenches and island arcs or mountain belts. E a r l y supporters of continental drift emphasized the remarkable fit between South America and Africa. Evidence showing t h a t rocks in matching parts of South America and Africa are of equal age is given b y P. M. H u r l e y and J. 1~. Rand. Evidence for the fit between the Maritime Appalachians of Canada and the British Caledonides is given in a paper by J . Dewey and M. Kay. Certainly some of the most convincing evidence for continental drift comes from the polar wandering paths derived from paleomagnetism. Although a paper by E. Irving and W. A. Robertson giving some results is included in this volume, the paleomagnetie work does not seem to have received the emphasis in this volume t h a t it deserves. Papers on the correlation between paleoclimatic evidence and paleomagnetic evidence are given by J. C. Briden and F. G. Stehli, and evidence related to continental movements from paleontology is given by A. J. Boucot, W. B. N. Berry, and J . G. Johnson. One of the most important discoveries in the evolving story of continental drift was the correlation by F. J. Vine and D. H. Matthews (Nature 199, 947, 1963) of the striped magnetic anomaly patterns parallel to oceanic ridges with the reversals of the E a r t h ' s magnetic field. Discussions of this correlation and the conclusions drawn from it are given in papers by F. J. Vine and J . R. Heirtzler. Discussions of the independent evidence for the time reversals of the E a r t h ' s magnetic field are given in papers by A. Cox, R. R. Doell, and G. B. Dalrymple, and by N. D. Updyke. The magnetic anomaly patterns are strong supporting evidence for the hypothesis of sea floor spreading. A summary of the seismic evidence supporting this hypothesis is given in a paper by L. R. Sykes. I n particular, evidence is given for the presence of transform faults and for horizontal motions having formed the Gulf of Aden, the R ed Sea, and the Gulf of California. The most widely accepted mechanism for largescale continental m o v e m e n t s is cellular convection in a viscous mantle. R. K. McDonald gives a discussion of the viscosity of the mantle from uplift data and flattening of the geoid. A discussion of the possible physical mechanisms for a viscous mantle is given by D. P. MeKenzie. Although no detailed discussions of mantle convection are included in this volume, H. W. Menard does present some of the problems of a convection model. In particular he mentions the possible migration of oceanic ridges and their
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associated convection cells. The chemical composition of the upper mantle is discussed by P. W. Gast. The quality of the papers presented in this volume is certainly high and the publishers are to be commended for doing an outstanding job at a relatively modest price. D. L. T~coa~rE Graduate School of Aerospace Engineering Co, nell University Ithaca, New York 14850
Symposium on Unidentified Flying Objects. Hearings before the Committee on Science and Astronautics, U.S. House of Representatives, 19th Congress, 2nd Session, J u l y 29, 1968. Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. iv ÷ 247 pp. Price $3.00. The report of this one-day symposium consists of the testimony and written reports of six scientists, who appeared in person before the Committee; and the prepared written papers from six additional scientists, who were not invited to be present in person. Chairman for the Symposium was Hen. J. Edward Roush. Although not stated in so m a n y words, it is fairly evident that one of the reasons for organizing this symposium was dissatisfaction in some quarters with the operation of Project Blue Book, U.S. Air Force, and the unfortunate breakdown in public relations t h a t had developed in connection with the investigation of U F O s being carried out at the University of Colorado under the direction of Dr. Edward U. Condon. I t was rather pointedly stressed on several occasions t h a t the symposium should not discuss either of the above-named projects. The six scientists who appeared in person were Dr. J. Allen Hynek, astronomer; Dr. J a m e s E. McDonald, physicist; Dr. Carl Sagan, astronomer; Dr. Robert L. Hall, sociologist; Dr. J a m e s A. Harder, engineer; and Dr. Robert M. L. Baker Jr., engineer. A study of previously published statements by this group suggests t h a t it was rather heavily weighted in favor of those who have been pressing for more aggressive action in the study of U F O s by the government of the U.S.A. In the statements made before the committee only one of the six, Dr. Sagan, expressed reservations re the value to science of using large sums of money in an expanded U F O study. I n tote, m a n y interesting points were brought up, and these hearings are worth reading by those who want to follow this subject in detail and to learn the various shades of opinion held.
BOOK REVIEWS
r e q u i r e d for t h e i r p r o d u c t i o n , a n d t h e n s a y s : " S u c h p r e s s u r e s axe t o o s m a l l t o b e c o n s i s t e n t with the parent-body radii...". Parent bodies in t h e 100 k m r a n g e of r a d i i as c o n s i d e r e d i n t h e discussion w o u l d h a v e c e n t r a l p r e s s u r e s o f t h e o r d e r o f 0.5 kilobaxs a n d , t h u s , t h e a b o v e m e n t i o n e d p r e s s u r e s are t o o large, n o t " t o o s m a l l " for t h e s e bodies, a m i s l e a d i n g a n d r a t h e r p u z z l i n g lapsus linguae. H e also does n o t i n d i c a t e t h e b a s i s for t h e e s t i m a t e s o f r a d i i of t h e p a r e n t bodies which depend on hypothetical heating and cooling t i m e s a n d are of n o a v a i l i f t h e b r e a k u p in collisions h a p p e n e d a t a n e a r l y e p o c h o f t h e prep l a n e t a r y stage. Collison t i m e s , n o t h e a t i n g or cooling times, w o u l d b e decisive. T h e d i a m o n d s , as well as t h e W i d m a n s t / i t t e n p a t t e r n , c o u l d t h e n b e easily reconciled w i t h s u b l u n a r size b o d i e s of a b o u t 1000 k m radius, m o d e r a t e l y h e a t e d i n r a p i d a c c r e t i o n a n d b r o k e n u p soon a f t e r f o r m a tion, w i t h c e n t r a l p r e s s u r e s a n d t e m p e r a t u r e s o f t h e o r d e r of 50 k b a n d 600°K, r e s p e c t i v e l y . T h e proposed production of diamonds in Canyon D i a b l o b y m e r e s h o c k a t i m p a c t looks like a m e c h a n i c a l i m p o s s i b i l i t y - - t h e t i m e is t o o s h o r t , a n d t h e r e q u i r e d h i g h p r e s s u r e s w o u l d h a v e led t o complete destruction of the specimens. The Canyon Diablo meteorites can only be fragments f r o m t h e r e a r o f t h e m a i n b o d y w h i c h were t h u s p r e s e r v e d f r o m t h e a p p l i c a t i o n of t o o h i g h pressures. I n his c o s m o g o n y t h e a u t h o r also cites t h e ' H a y a s h i c o n t r a c t i v e p h a s e " of s t a r f o r m a t i o n ' as s o m e t h i n g s e l f - e v i d e n t a n d b e l o n g i n g to t h e h a r d w a r e of a s t r o p h y s i c s . Y e t t h i s p h a s e , following u p t h e collapse of a g r a v i t a t i o n a l i n s t a b i l i t y i n a gaseous m e d i u m , p r o b a b l y n e v e r d i d t a k e place in t h e solar s y s t e m . E v e n a t as low a t e m p e r a t u r e as 4°K, f o r m a t i o n of a solar m a s s t h r o u g h s p o n t a n e o u s c o n t r a c t i o n of t h e i n s t a bilities w o u l d r e q u i r e a n i n i t i a l d e n s i t y i n t h e p a r e n t n e b u l a of a b o u t 2.5 × 10 -21 g m / c m 3, 1000 t i m e s h i g h e r t h a n in t h e i n t e r s t e l l a r m e d i u m . A t 100°K, t h e d e n s i t y w o u l d e x c e e d 4 x 10-17gin/ c m 3. N o w h e r e i n t h e spiral a r m s , or i n t h e cosmic clouds (where s t a r s are seen t o o r i g i n a t e curr e n t l y ) c o u l d s u c h c o n d e n s a t i o n s t a k e place, exc e p t t h r o u g h p r e l i m i n a r y f o r m a t i o n of nuclei f r o m t h e solid c o n t e n t s of space, w h i c h t h e n w o u l d g r o w b y a c c r e t i o n , n u t collapse. T h e article o n p u l s a r s b y T h o r n e is clear a n d b r o u g h t to t h e level o f g r a d u a t e s t u d e n t s , despite s u c h i n v o l v e d s u b j e c t s as g e n e r a l r e l a t i v i t y effects a n d g r a v i t a t i o n a l r a d i a t i o n . I t is easier t o s h o w w h a t t h e p u l s a r s are n o t t h a n w h a t t h e y a r e ; n e v e r t h e l e s s , in t h e case of t w o p u l s a r s w i t h a s t a b l e p e r i o d a r o u n d 1 sec a n d a less s t a b l e one of a b o u t 0.01 sec, a good w o r k i n g h y p o t h e s i s is t h a t of a n e u t r o n s t a r r o t a t i n g w i t h a p e r i o d of 1 sec a n d s i m u l t a n e o u s l y p u l s a t i n g in 0.01 sec. I t s
m a s s w o u l d b e 0.1-0.2 solar masses, t h e r a d i u s 50 t o 200 k m , t h e c e n t r a l d e n s i t y 3 × 1013 t o 1014 g m / e m s, b e i n g h i g h l y c e n t r a l l y c o n d e n s e d w i t h a large diffuse e n v e l o p e . I n M o t i o n s i n t h e A t m o s p h e r e of J u p i t e r , b y R . M. Goody, t h e r e is t o o m u c h u n e x p l a i n e d j a r g o n t o b e followed u p b y a n a v e r a g e g r a d u a t e s t u d e n t of a s t r o p h y s i c s . " A c c e l e r a t i o n " is h e r e u s e d i n t h e sense o f difference i n t h e a n g u l a r velocity of rotation, and not in its ordinary s e n s e - - a t r i v i a l t h i n g for p l a n e t a r y observers, b u t n o t for novices. A n d w h a t is " T h e Coriolis parameter" ?--there could be several of them. T h e w e l l - w r i t t e n article b y B u r b i d g e o n t h e g a l a c t i c m a g n e t i c field, d e s p i t e all t h e u n c e r t a i n ires of i n t e r p r e t a t i o n , l e a v e s one w i t h t h e imp r e s s i o n t h a t t h e g e n e r a l field is m u c h w e a k e r t h a n f o r m e r l y s u p p o s e d , p e r h a p s o n l y of t h e o r d e r of 10 -6 gauss, b u t t h a t t h e g a l a c t i c r a d i o e m i s s i o n w h i c h r e q u i r e d a s t r o n g e r field "is m a d e u p largely of r a d i a t i o n f r o m d i s c r e t e s o u r c e s . " T h e article b y Dessler o n t h e solar w i n d is also clear e n o u g h t o b e u n d e r s t o o d b y t h e n o n i n i t i a t e d . I n a d v o c a t i n g t h e h y d r o d y n a m i c flow s o l u t i o n for t h e solar w i n d , he, h o w e v e r , fails t o s h o w t h e source o f e n e r g y i n t h e e x p a n s i o n . U n l e s s t h e i n i t i a l t e m p e r a t u r e is i t s e l f sufficient a n d of t h e o r d e r of 2 × 107 °K, t e n t i m e s h i g h e r than the coronal temperature, conductivity of the hot plasma must be advocated to heat up the gas c u r r e n t l y . I f t h i s were n o t so, t h e a b i l i t y of t h e hydrodynamic stream to escape the gravitational field o f t h e S u n w o u l d look like a k i n d ofperpe-
tuum mobile. T h e m e r e f a c t t h a t t h i s first issue of t h e n e w " C r i t i c a l J o u r n a l " h a s p r o v o k e d h e r e n e w chall e n g i n g c o m m e n t s or e v e n d i s s e n t m a y b e reg a r d e d as a n i n d i c a t i o n t h a t i t h a s s e r v e d its p u r p o s e well in s t i m u l a t i n g critical t h o u g h t .
E. J. 0PIK
Dept. of Physics and Astronomy University of Maryland, College Park, Maryland and Armagh Observatory, Northern Ireland The History of the Earth's Crust. Edited by R . A. P H I ~ . Y . P r i n c e t o n U n i v e r s i t y Press, P r i n c e t o n , N e w J e r s e y , 1968. 244 pp. P r i c e $13.50. This book includes papers presented at a s y m p o s i u m o n T h e H i s t o r y o f t h e E a r t h ' s Crust h e l d a t t h e G o d d a r d I n s t i t u t e for Space S t u d i e s i n N o v e m b e r , 1966. U n f o r t u n a t e l y i t h a s required t w o y e a r s t o p u b l i s h t h e s e p r o c e e d i n g s ; in a r a p i d l y d e v e l o p i n g field t h i s seriously det r a c t s f r o m t h e v a l u e of a p u b l i c a t i o n . B a s i c a l l y
BOOK REVIEWS the contents of the book present the evidence supporting continental drift and sea floor spreading. I9o discussion is included of either ocean trenches and island arcs or mountain belts. E a r l y supporters of continental drift emphasized the remarkable fit between South America and Africa. Evidence showing t h a t rocks in matching parts of South America and Africa are of equal age is given b y P. M. H u r l e y and J. 1~. Rand. Evidence for the fit between the Maritime Appalachians of Canada and the British Caledonides is given in a paper by J . Dewey and M. Kay. Certainly some of the most convincing evidence for continental drift comes from the polar wandering paths derived from paleomagnetism. Although a paper by E. Irving and W. A. Robertson giving some results is included in this volume, the paleomagnetie work does not seem to have received the emphasis in this volume t h a t it deserves. Papers on the correlation between paleoclimatic evidence and paleomagnetic evidence are given by J. C. Briden and F. G. Stehli, and evidence related to continental movements from paleontology is given by A. J. Boucot, W. B. N. Berry, and J . G. Johnson. One of the most important discoveries in the evolving story of continental drift was the correlation by F. J. Vine and D. H. Matthews (Nature 199, 947, 1963) of the striped magnetic anomaly patterns parallel to oceanic ridges with the reversals of the E a r t h ' s magnetic field. Discussions of this correlation and the conclusions drawn from it are given in papers by F. J. Vine and J . R. Heirtzler. Discussions of the independent evidence for the time reversals of the E a r t h ' s magnetic field are given in papers by A. Cox, R. R. Doell, and G. B. Dalrymple, and by N. D. Updyke. The magnetic anomaly patterns are strong supporting evidence for the hypothesis of sea floor spreading. A summary of the seismic evidence supporting this hypothesis is given in a paper by L. R. Sykes. I n particular, evidence is given for the presence of transform faults and for horizontal motions having formed the Gulf of Aden, the R ed Sea, and the Gulf of California. The most widely accepted mechanism for largescale continental m o v e m e n t s is cellular convection in a viscous mantle. R. K. McDonald gives a discussion of the viscosity of the mantle from uplift data and flattening of the geoid. A discussion of the possible physical mechanisms for a viscous mantle is given by D. P. MeKenzie. Although no detailed discussions of mantle convection are included in this volume, H. W. Menard does present some of the problems of a convection model. In particular he mentions the possible migration of oceanic ridges and their
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associated convection cells. The chemical composition of the upper mantle is discussed by P. W. Gast. The quality of the papers presented in this volume is certainly high and the publishers are to be commended for doing an outstanding job at a relatively modest price. D. L. T~coa~rE Graduate School of Aerospace Engineering Co, nell University Ithaca, New York 14850
Symposium on Unidentified Flying Objects. Hearings before the Committee on Science and Astronautics, U.S. House of Representatives, 19th Congress, 2nd Session, J u l y 29, 1968. Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. iv ÷ 247 pp. Price $3.00. The report of this one-day symposium consists of the testimony and written reports of six scientists, who appeared in person before the Committee; and the prepared written papers from six additional scientists, who were not invited to be present in person. Chairman for the Symposium was Hen. J. Edward Roush. Although not stated in so m a n y words, it is fairly evident that one of the reasons for organizing this symposium was dissatisfaction in some quarters with the operation of Project Blue Book, U.S. Air Force, and the unfortunate breakdown in public relations t h a t had developed in connection with the investigation of U F O s being carried out at the University of Colorado under the direction of Dr. Edward U. Condon. I t was rather pointedly stressed on several occasions t h a t the symposium should not discuss either of the above-named projects. The six scientists who appeared in person were Dr. J. Allen Hynek, astronomer; Dr. J a m e s E. McDonald, physicist; Dr. Carl Sagan, astronomer; Dr. Robert L. Hall, sociologist; Dr. J a m e s A. Harder, engineer; and Dr. Robert M. L. Baker Jr., engineer. A study of previously published statements by this group suggests t h a t it was rather heavily weighted in favor of those who have been pressing for more aggressive action in the study of U F O s by the government of the U.S.A. In the statements made before the committee only one of the six, Dr. Sagan, expressed reservations re the value to science of using large sums of money in an expanded U F O study. I n tote, m a n y interesting points were brought up, and these hearings are worth reading by those who want to follow this subject in detail and to learn the various shades of opinion held.