464 Notices respecting New Books. 



actnal note of the pipe, when blown in the ordinary way by a 

 wind of pressure measured by 2 \ inches of water, corresponded 

 to an effective length of 28 inches, so that the blown note was 

 actually higher in pitch than the note of maximum resonance. 

 So far, therefore, from the depression of pitch in an organ- 

 pipe below that calculated from the actual length, according to 

 Bernoulli's theory, being principally due to the action of the 

 wind, it would appear that in the absence of a peculiar action 

 of the wind the depression would be even greater than it is. 

 Too much stress, however, must not be laid on a single obser- 

 vation; and all I would maintain is, that by far the larger part 

 of the depression of pitch is due to the insufficient openness 

 of the lower end of the pipe. 



May 9, 1877. 



LXII. Notices respecting New Boohs. 



The Elements of Machine Design : an Introduction to the Principles 

 which determine the Arrangement and Proportion of the Parts of 

 Machines, and a Collection of Rules for Machine Design. By 

 W. Cawthok^e Unwin, B. Sc, Assoc. Inst. Civil Engineers, 

 Professor of Hydraulic and Mechanical Engineering at the Royal 

 Indian Civil Engineering College. London : Longmans, Green, 

 and Co., 1877. [Text-Books of Science, small 8vo. Pp. 326.] 

 nPHE author takes as a motto for his work an extract from 

 Beuleaux's ' Theoretical Kinematics,' of which the following is 

 part: — "Machine design has been removed by Eedtenbacher from 

 its incorrect position as a part of Applied Mechanics, and established 

 on a footing of its own. Its province is to show how the parts of 

 the machine are to be proportioned so as to resist deformation. 

 In order to accomplish this fully, they must be considered both 

 with reference to the external forces acting on the machine, and 

 the corresponding molecular forces within its substance." These 

 words serve as a general description of the author's aim; and 

 accordingly he begins the volume with an account of the theory of 

 the strength of materials, with a view to its application to the 

 questions which form the subject of the volume. These may be 

 briefly enumerated as fastenings, pipes, shafts, bearings, gearing, 

 linkwork, and valves. It is almost needless to say that, though to 

 ensure a due degree of strength is an important element in design- 

 ing machinery, many other points are brought under notice ; and 

 accordingly the work is not so exclusively occupied with the ques- 

 tion of strength as the motto might lead the reader to expect. 

 Thus, in the chapter on toothed gearing, our author first considers 

 the cases of shafts driven by rolling contact, and proceeds to show 

 the need of teeth for transmitting force by this means. After 

 briefly mentioning the materials employed, he defines the parts 

 and proportions of teeth, investigates the conditions which deter- 



