62 Notices respecting New Books. 



A smaller cell made to fit into the wooden frame of a lantern- 



Fig. 2. 



slide (fig. 2), which has attached 

 to it platinum wires connected 

 by copper wires and binding- 

 screws with a galvanic battery, 

 serves to project electrolytic de- 

 compositions upon the screen. 

 Perhaps the most beautiful ap- 

 pearance is that presented by the crystallization of the metal 

 from a solution of lead-acetate which is undergoing electrolysis*. 

 In order that the cell may be water-tight, it is necessary that 

 the india-rubber rings should exert a somewhat powerful com- 

 pression; but even under favourable circumstances slight 

 leakage is liable to occur in about half an hour after the cell 

 has been filled ; this, however, would allow ample time for the 

 display of any of the phenomena above alluded to. Rings cut 

 from large-sized india-rubber tubing have been found well 

 adapted for the construction of small cells. 



X. Notices respecting New Books. 



Text-Boohs of Science. — Principles of Mechanics. By T. M. Good- 

 ewe, M.A., Lecturer on Applied Mechanics at the Royal School of 

 Mines. London: Longmans, Green, and Co. 1874 (small 8vo, 

 pp. 313). 

 HPHIS book contains an exposition of the principles of mechanics, 

 -*■ such as is commonly given in elementary treatises on that science. 

 The exposition is illustrated in two ways — -first by means of exam- 

 ples of the ordinary type, secondly by reference to actual mecha- 

 nical contrivances mainly of a modern character. There are about 

 a hundred and eighty illustrations of the former kind ; and of these 

 about one in every four is taken from the Science Examination 

 papers drawn up for the annual exam in ations of the Department 

 of Science and Art. The second class of illustrations constitutes 

 the chief peculiarity of the book, and unquestionably its most valu- 

 able part. The mere names of some of these illustrations will be 

 enough to show this — e. g. the carrying of com on bands, the feed- 

 ing of running trains with water, the disintegrating flour- mill , the 

 ventilation of coal-mines, the lifting of coals, the stone-crushing 

 machine, Weston's friction coupling, the break-drum, the crown 

 valve, the blowing-engine, the hydraulic accumulator, the hydraulic 

 crane, &c. These form an assemblage of contrivances which have 

 never before, to our knowledge at least, been described in any ele- 

 mentary book ; they render the work before us worthy of the study 

 of all who are interested in mechanical science; and we do not 



* Mr. W. Crookes, F.E..S., suggests the electrolysis of solution of thal- 

 lium sulphate as furnishing a still more beautiful example of crystallization. 



