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Fossil oak
140
5I~'ansm~sion by Electricity.
[aour. Frank. Ir~t,,
F o s s i l 0 a k . - - A sunken oak fiwest, of great extent, has been lately" discovered ill the neighborh(~od of Rot lmnburg, on tim Fulda, in HesseCa.~set, from two to three meters (6"562 to .q'8-13 I'L) 1)clew the surface. I t appears to haw', been submerged in prehistoric times, in consequence of heavy t>eshets on the Fulda. Some of the trunks are of truly colossal dimensions. The wood is teaM)lack and e×traordinarily hard.
--l~brtschr. der Zeit.
C.
The N a v i s p h e r e . - - M . de Magnae has submitted to the French Academy an instrument tbr navigators, to which he gives the nmne o f navisphere. It shows the stars which are above tile horizon at any gi yen morn ent, and determ i~es their al ti tudes and azim uths with in about; 1 °. It also shows, with the .~une approximation, the proper course for great-circle sailing fi'om one point to another, and the distance between those points within about ~ of 1 o. i t gives a ready practical solution of spherical triangles. It has been tried upon the Washing#m, of the Transatlantic Company, with such i:avorable results that it seems likely to come into general use. l i t wouht be interesting and desirable to subject it to comparative tests with Dr. Thoma.s Hill's Nautrigon.]~ Compte,s Rendus.
C.
Transmission of Force by Eleetricity.--In an extended communication "On the transmission and distribution of motive power to a great distance by means of electricity," M. A. Aehard cites experiment.s of MM. Higgs and Brattle, and of E. I-Iagenbueh-Bisehoff, Professor of Physics in tile University of Basle. The gentlemen first named used Siemens' machines, and found a maximum efficiency o f t'rom 39 to 49 per cent. when the rotating velocity of the receiver was about half as great ms that of the generator. M. Hagenbueh-Bisehoff experimented with a Gramme machine, and reported eitieiency of from 65"9 to 93'5 per cent., the three being inerea,~ed by the aid of a brake, a method which Aehard thinks objectionable. He recommends systematic experiments fbr the fbllowing purposes: 1. To ascertain, for many types of induction maehines~ and for the principal varieties o f each type, the relation between the intensity" of the current and the magnetism of the induction magnet.% and to seek an empirical tbrmula for representing the relation. 2. To determine the rendering of the different induction machines when acting as generators. 3. To determine the rendering of the rome maehlnes when acting am m o t o r s . ~ A~n. des Mines. C.
5I~'ansm~sion by Electricity.
[aour. Frank. Ir~t,,
F o s s i l 0 a k . - - A sunken oak fiwest, of great extent, has been lately" discovered ill the neighborh(~od of Rot lmnburg, on tim Fulda, in HesseCa.~set, from two to three meters (6"562 to .q'8-13 I'L) 1)clew the surface. I t appears to haw', been submerged in prehistoric times, in consequence of heavy t>eshets on the Fulda. Some of the trunks are of truly colossal dimensions. The wood is teaM)lack and e×traordinarily hard.
--l~brtschr. der Zeit.
C.
The N a v i s p h e r e . - - M . de Magnae has submitted to the French Academy an instrument tbr navigators, to which he gives the nmne o f navisphere. It shows the stars which are above tile horizon at any gi yen morn ent, and determ i~es their al ti tudes and azim uths with in about; 1 °. It also shows, with the .~une approximation, the proper course for great-circle sailing fi'om one point to another, and the distance between those points within about ~ of 1 o. i t gives a ready practical solution of spherical triangles. It has been tried upon the Washing#m, of the Transatlantic Company, with such i:avorable results that it seems likely to come into general use. l i t wouht be interesting and desirable to subject it to comparative tests with Dr. Thoma.s Hill's Nautrigon.]~ Compte,s Rendus.
C.
Transmission of Force by Eleetricity.--In an extended communication "On the transmission and distribution of motive power to a great distance by means of electricity," M. A. Aehard cites experiment.s of MM. Higgs and Brattle, and of E. I-Iagenbueh-Bisehoff, Professor of Physics in tile University of Basle. The gentlemen first named used Siemens' machines, and found a maximum efficiency o f t'rom 39 to 49 per cent. when the rotating velocity of the receiver was about half as great ms that of the generator. M. Hagenbueh-Bisehoff experimented with a Gramme machine, and reported eitieiency of from 65"9 to 93'5 per cent., the three being inerea,~ed by the aid of a brake, a method which Aehard thinks objectionable. He recommends systematic experiments fbr the fbllowing purposes: 1. To ascertain, for many types of induction maehines~ and for the principal varieties o f each type, the relation between the intensity" of the current and the magnetism of the induction magnet.% and to seek an empirical tbrmula for representing the relation. 2. To determine the rendering of the different induction machines when acting as generators. 3. To determine the rendering of the rome maehlnes when acting am m o t o r s . ~ A~n. des Mines. C.