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Mechanics for beginners
May, I935.]
BOOK ][~EVIEWS.
655
in 1933. Newsprint forms the bulk of the tonnage. Newsprint production in the United States has had a much more stable course. The pulp and paper industry contributed approximately $98,ooo,ooo in 1932 and $9o,ooo,ooo in I933 toward the production of a favorable Canadian trade balance. Products of forest origin have always been more dependable from the point of view of sustaining favorable trade balances than any other comparable group of commodities. LESLIE R. BACON. MECHANICS FOR BEGINNERS. By F. Barraclough, M.A., and E. J. Holmyard, M.A., M.Sc., D.Litt., F.I.C. With 92 figures and 8 plates. 214 pages, i 2 . 2 X i8.o cm. Dent's Modern Science Series. London. J . M . Dent and Sons, Ltd., (E. P. Dutton & Co., Inc., New York). Price $I.OO. As a first book in mechanics this little volume should prove a reasonable success. It is judged to approximate American secondary schools in advancement of treatment. The informal style catches and holds the interest without resort to extravagant window-dressing. General principles are illustrated by examples common to the experiences of all readers. The following discussion of walking illustrates the general level of treatment: " T h e difficulty of learning to walk is simply the difficulty of learning how to move one's centre of gravity appropriately. There is no necessity to see a slowmotion film of a person walking to understand what happens: you can find out yourself. Put your left leg forward as you do in walking, but as slowly as possible. You will discover t h a t you fall on to this foot, and have made one step forward in consequence. W h a t has happened is clear. One part of you, viz. your leg, was moving forwards, and your centre of gravity was thus also advancing. Ultimately the vertical line through your center of gravity passed beyond your right foot, so t h a t no upward force of the floor could then act through it. As a result, you overbalanced on to your left foot. Walking is simply a succession of such acts." The several chapters take up forces, moments, center of gravity, work, machines, density and specific gravity, liquid pressure, gases, speed, velocity, acceleration, Newton's Laws of Motion and a little about energy. Thus the reader is left in possession of considerable real knowledge. Much care has evidently been used to avoid creation of misapprehensions, though Heaven alone knows how much the Bible itself is subject to misinterpretation. LESLIE R. BACON. PRACTICAL SOLUTION OF TORSIONAL VIBRATION PROBLEMS, WITH EXAMPLES FROM MARINE, ELECTRICAL, AND AUTOMOBILE ENGINEERING PRACTICE, by W. Ker Wilson, M.Sc. 438 pages, illustrations, tables, 14 X 22. 5 cms. New York, John Wiley & Sons, Inc., 1935. Price $7.oo. The ever increasing demand for the performance of work by rotating machinery brings forth a multitude of problems dealing with rotation of shafts. It is necessary for the designers of this machinery to take into account from every possible angle all t h a t affects its workability and permanency. Much depends, now-a-days, on accuracy of design. As a result sharp focus is centered on every factor. Torsional vibration is one of these factors which demands expert knowledge. The book at hand is an instrument by which it is possible to select data appropriate to particular problems. A set of standard forms suitable for rapid reference can then be built up.
BOOK ][~EVIEWS.
655
in 1933. Newsprint forms the bulk of the tonnage. Newsprint production in the United States has had a much more stable course. The pulp and paper industry contributed approximately $98,ooo,ooo in 1932 and $9o,ooo,ooo in I933 toward the production of a favorable Canadian trade balance. Products of forest origin have always been more dependable from the point of view of sustaining favorable trade balances than any other comparable group of commodities. LESLIE R. BACON. MECHANICS FOR BEGINNERS. By F. Barraclough, M.A., and E. J. Holmyard, M.A., M.Sc., D.Litt., F.I.C. With 92 figures and 8 plates. 214 pages, i 2 . 2 X i8.o cm. Dent's Modern Science Series. London. J . M . Dent and Sons, Ltd., (E. P. Dutton & Co., Inc., New York). Price $I.OO. As a first book in mechanics this little volume should prove a reasonable success. It is judged to approximate American secondary schools in advancement of treatment. The informal style catches and holds the interest without resort to extravagant window-dressing. General principles are illustrated by examples common to the experiences of all readers. The following discussion of walking illustrates the general level of treatment: " T h e difficulty of learning to walk is simply the difficulty of learning how to move one's centre of gravity appropriately. There is no necessity to see a slowmotion film of a person walking to understand what happens: you can find out yourself. Put your left leg forward as you do in walking, but as slowly as possible. You will discover t h a t you fall on to this foot, and have made one step forward in consequence. W h a t has happened is clear. One part of you, viz. your leg, was moving forwards, and your centre of gravity was thus also advancing. Ultimately the vertical line through your center of gravity passed beyond your right foot, so t h a t no upward force of the floor could then act through it. As a result, you overbalanced on to your left foot. Walking is simply a succession of such acts." The several chapters take up forces, moments, center of gravity, work, machines, density and specific gravity, liquid pressure, gases, speed, velocity, acceleration, Newton's Laws of Motion and a little about energy. Thus the reader is left in possession of considerable real knowledge. Much care has evidently been used to avoid creation of misapprehensions, though Heaven alone knows how much the Bible itself is subject to misinterpretation. LESLIE R. BACON. PRACTICAL SOLUTION OF TORSIONAL VIBRATION PROBLEMS, WITH EXAMPLES FROM MARINE, ELECTRICAL, AND AUTOMOBILE ENGINEERING PRACTICE, by W. Ker Wilson, M.Sc. 438 pages, illustrations, tables, 14 X 22. 5 cms. New York, John Wiley & Sons, Inc., 1935. Price $7.oo. The ever increasing demand for the performance of work by rotating machinery brings forth a multitude of problems dealing with rotation of shafts. It is necessary for the designers of this machinery to take into account from every possible angle all t h a t affects its workability and permanency. Much depends, now-a-days, on accuracy of design. As a result sharp focus is centered on every factor. Torsional vibration is one of these factors which demands expert knowledge. The book at hand is an instrument by which it is possible to select data appropriate to particular problems. A set of standard forms suitable for rapid reference can then be built up.