622 



NA TURE 



[October 24, 1901 



the activity and utility of its members. It is true that 

 very many of these are obtained from the surface of the 

 sea and not strictly from the shore, but that same remark 

 applies equally to the medusoids discussed and figured 

 in Chapter iii., and it would be difficult to catch the 

 medusoids without seeing Copepoda also. But there are 

 also plenty of shore-haunting copepods to be obtained 

 very easily with a muslin hand-net in pools, or from sand 

 and mud at low tide, and under stones. A small boy of 

 six has just brought me a cup full of bright red ones 

 {Harpacticus fulvus) which he caught himself with a 

 sixpenny hand-net along the edge of the sea and in 

 pools, where they are quite visible to the eye. He 

 wanted to know what they were and how they jumped, 

 and his little sister of two-and-a-half added the important 

 question, " Why are they so red.'" If Miss Newbigin 

 would answer these questions — and no one is more com- 

 petent than she to deal with the last one — it wouldthelp 

 not only the children, but their seniors. Harpacticus is 

 sometimes very abundant in pools far up the shore, 

 where their red bodies are quite conspicuous on the green 

 Entcromorpha, and they are eaten with avidity by young 

 blennies, sticklebacks and other little shore fishes. 

 " Why are ihcy so red ? " ' 



The " keys for identification " and other similar tables 

 of characters at the ends of chapters are of doubtful 

 utility. They are, of course, incomplete ; they only deal 

 with a few selected genera and species in each section, 

 and yet from their form they give the deceptive impres- 

 sion of a complete classification ; they lead to a good deal 

 of repetition and give little information beyond what is 

 in the text — a considerable saving of space would be 

 effected by their removal. What is the difference between 

 ' "legs very slender and long" given as a character of 

 Pho.xichilidium, and " legs very long and slender " as a 

 character of Nymphon in the table on p. 224 .? 



Dissection of the types chosen and details of internal 

 structure have, probably quite wisely, been avoided ; but 

 under those circumstances some statements in the book, 

 such as that "the heart is in front of the gill" (p. 24S) 

 given as a character of the opisthobranchs, will probably 

 be found meaningless to readers without further know- 

 ledge than the book gives. Even one simple anatomical 

 diagram of the type form of each group would have been 

 a useful addition. 



There are, of course, other points of detail in connec- 

 tion with which alterations might be suggested. Astcriiia 

 gihhosa, very common in shore pools amongst Coralliiia 

 on some parts of the coast, might be added to the star- 

 fishes discussed. The presence of thread-cells in the 

 cerata oi Eolis is an interesting point worthy of mention. 

 Trochus zizyphini/s (p. 236) is not merely an inhabitant 

 of deep water, but is common, alive, between tide-marks 

 on some of our shores. On the whole the figures are 

 good, but Alcyoiiium (p. 16), Polycarpa (p. 295) and 

 Pleiirobrachia (p. 330) are not satisfactory. 



The style of the book is easy and pleasing— lively even 

 in places, as on p. 277, where the author describes how 

 she first made acquaintance with the grace and beauty of 

 the living Lima hians when released from its woven nest 

 of shells and weeds. In conclusion, it is a pleasure to 



nKr,2Ir'?1^V"'^lK "•'' '""^ ■'■"i'' °f answer-the OM in terms of lipo- 

 chromes and the other m terms of natural selection. 



NO. 1669, VOL. 64] 



cordially recommend " Life by the Sea-shore" as a I 



charming and useful holiday companion which will not 1 



only give much information, but will also serve as a j 



good introduction to one of the most fascinating branches ! 



of modern science. W. .\. Herdman. ,1 



SCIENTIFIC TOPOGRAPHY. 

 Recherches siir les instruments, les methodcs et le dessin 



Topographiqites. By Colonel A. Laussedat. Tome ii. 



Parti. Pp.198. (Paris : Gauthier-\'illarset Fils, 1901.) 

 T N the first part of the second volume of his exhaustive 

 -L treatise on topography. Colonel Laussedat treats of 

 " iconometrie" and " m^trophotographie " — two branches 

 of the art which are but little studied in British military 

 schools. He commences by tracing the evolution of the 

 photo-theodolite from the primitive forms of the camera 

 obscura and the camera lucida ; and not the least instruc- 

 tive part of this volume is to be found in the carefiil 

 analysis of those principles of perspective which are the 

 governing principles of all methods of reducing a field 

 of observation to its horizontal plan, whether for the 

 purpose of topography or of plan drawing. He shows 

 that the camera lucida is an instrument which (in France 

 at any rate) has proved of immense value in the hands 

 of the military engineer. Some excellent examples are 

 given by Colonel Laussedat of the practical use that has 

 been made of this instrument in the construction of accu- 

 rate geometrical views of fortifications, with the object 

 of obtaining precise plans of the same, on the principle 

 which was first advocated by Beautemps-Beaupre, and 

 which is fully explained by the author. It is curious 

 that an English invention (it was invented in 1804 by 

 Wollaston) should have been applied to so much greater 

 practical purpose in France than it ever has been in 

 England. 



From camera lucida drawings of the elevation of a 

 line of fortifications, or of buildings taken from two or 

 more points of view, French engineers have found it 

 possible to construct accurate plans of the same fortifi- 

 cations on precisely the same principles which now lead 

 to the definition of topography from photographs. 

 With this instrument, combined with a telescopic enlarge- 

 ment of the field of view, the defenders of Paris during 

 the last memorable siege were able to construct a fairly 

 accurate panorama of the German advanced positions 

 around the city, to note the daily and hourly changes in 

 those positions, and to keep the military authorities 

 perpetually supplied with most important information 

 which would otherwise have been impossible to attain. 

 In his concluding chapter Colonel Laussedat renders a 

 well-deserved tribute of recognition to those many 

 assistants (astronomers, doctors, engineers, artists and 

 architects) who all brought the necessary technical artistic 

 skill to his assistance and maintained that remarkable 

 record. In England the camera lucida is still recognised 

 as an important aid to the illustration of geological 

 phenomena. But its capabilities as a military instrument 

 have been hardly recognised. 



From the camera lucida to the photo-theodolite is a 

 natural process of evolution, and the best half of the 

 volume is devoted to its illustration. The application of 

 photography to surveying has already been well tested 



