702 SCIENCE PROGRESS 



and many others are pretty exhaustively treated, it is remarkable how few they are. 



The most considerable omission is, perhaps, the absence of any exposition of 



Dr. Archdall Reid's speculative contributions to this subject. Again, cases cited 



as non-Mendelian have by now been brought in line with others which are 



understood. 



A. D. Darbishire. 



Hints for Crystal-drawing. By Margaret Reeks. With a Preface by John 

 W. Evans, D.Sc, LL.B., F.G.S. [Pp. 148 + xx.] With 5 figures and 44 

 plates. (London : Longmans, Green & Co., 1908.) 



The student who wishes to gain a proper comprehension of the aspect of crystals 

 possessing certain symmetry and bounded by particular groups of faces, must 

 acquire some facility in the correct delineation of crystals on paper. As Dr. Evans 

 points out in the preface which he has contributed, models are not readily available, 

 and, in any case, their use would not have such educational value as adequate train- 

 ing in crystal-drawing. Mineralogical text-books devote a chapter to this subject ; 

 but considerations of space permit of only a general discussion, which, because of 

 its brevity and the want of sufficient examples, may prove puzzling to many students 

 approaching the subject for the first time. Such readers should be grateful to 

 Miss Reeks for the thorough and comprehensive nature of what she modestly 

 calls hints. 



Pictures of crystals differ from both ordinary perspective and mathematical 

 drawings, and yet embrace the principles of both. To give as complete an idea of 

 the shape of the crystal as possible, something more than a plan is required, and to 

 retain the parallelism of edges, which is an expression of Haiiy's great law, the 

 plane of the paper must be supposed to be at an infinite distance from the eye. 

 The method generally followed by crystallographers is that adopted by Mohs nearly 

 a century ago in his treatise on mineralogy. The direction of any edge upon the 

 crystal is easily determined as soon as the positions of the fundamental axes and 

 the unit distances upon them have been found. How this important preliminary 

 step may be achieved by purely graphical means, even in the complex case of the 

 triclinic system, is lucidly explained by Miss Reeks. The understanding of the 

 text is greatly facilitated by the excellent plates which have been reproduced from 

 the author's own drawings. 



G. F. Herbert Smith. 



A Stndy of Splashes. By A. M. Worthington, C.B., F.R.S. [Pp. 129 + xii.] 

 (Longmans, Green & Co. 6s. bd. net.) 



Bv the aid of nearly two hundred instantaneous photographs systematically 

 arranged and beautifully reproduced, this book exhibits what happens when a 

 falling sphere meets and passes into a mass of liquid, originally at rest, under 

 various circumstances. 



The least eventful case occurs when the sphere is solid and smooth and when 

 the velocity at contact is not very great. Then the liquid rises rapidly round the 

 sphere and envelops it completely, like a " sheath," before it has sunk below the 

 original level of the fluid. When the sphere is rough, the splash does not follow 

 its surface, but rises round it like a bowl-shaped "basket." Afterwards this 

 subsides, and a tall, vertical jet of liquid rises from the bottom of the pit which the 

 falling sphere produces. 



If the velocity at contact is great enough, the basket-splash closes upon itself at 



