,i6 



NA TURE 



[August 3, 1905 



find as much about the one half of living nature as 

 about the other in it. 



The most fruitful source of progress is a new way 

 of looking at things, and such new points of view 

 result in the destruction of old classifications and the 

 need for new ones ; in biology, investigators will soon 

 cease to be classified according to the group of 

 animals or plants with which they deal, but accord- 

 ing to the particular phase of the problem of the 

 " fundamental nature of living things " (which is the 

 ultimate goal of biological inquiry) which interests 

 them. In the study of heredit)', for example, there 

 IS already a number of investigators who are as 

 familiar with that phenomenon in the case of animals 

 as in the case of plants. Nor does it seem reasonable 

 to doubt that, by thus broadening the basis of material 

 used by the investigator, the conclusions arrived at 

 by him are likely to be less wide of the truth than 

 they are apt to be if they are based on the result of 

 experiment with a single animal or plant. The moral 

 of this is, not that Prof, de Vries ought to have said 

 something about animals in his book, but that the 

 disappointed zoological reader ought to know some- 

 thing about plants for the sake of his work. 



To bestow praise on any work of Prof, de Vries 

 would be impertinent; to cite points of particular 

 Interest in the book is unnecessary, for it has already 

 tegun to form part of the indispensable equipment of 

 the student of evolution in the broadest sense of that 

 term. A. D. 



ASPHALT PAVEMENTS. 

 The Modern Asphalt Pavement. By Clifford Richard- 

 son. Pp. vii + 580. (New York: John Wiley and 

 Sons; London: Chapman and Hall, Ltd., 1905.) 

 Price I2S. 6d. net. 

 T^HLS is a book dealing with an important practical 

 subject which up to the present time has not 

 received much attention from writers of text-books. 

 Asphalt pavements of various kinds are now so largely 

 used that a text-book dealing with this subject has 

 been a long-felt want. 



The book is divided into sections, and the 

 author has appended to the end of each chapter a 

 brief summary of the matter dealt with, enabling the 

 reader to determine quickly whether or not the chapter 

 contains the information he is seeking for. The 

 first section deals with the construction of the road 

 base upon which the surface carrying the traffic is 

 supported, and it is evident that Mr. Richardson is 

 of opinion that the ideal base is hydraulic concrete. 

 Between this base and the surface proper is interposed 

 a binder, or intermediate, course ; where the traffic 

 is heavy, the best material for this is a layer of com- 

 pact asphaltic concrete. The next section is concerned 

 with the materials employed in making the asphalt 

 surface mixture, and a detailed account is given of 

 the sands used for this purpose and of their origin 

 and physical characteristics. After a brief explan- 

 ation and classification of the various hydrocarbons 

 of which native bitumen is composed, the author 

 describes the native bitumens which have so far been 

 used in paving work. 



NO. 1866, VOL. 72] 



In section iv. the technology of the paving industry 

 is taken up ; the preparation of the surface mixture 

 is explained with the help of elaborate tables, and the 

 theory which underlies the practical work is described ; 

 the author points out that an asphalt surface in order 

 to be successful must resist both weathering and 

 impact. The mechanical appliances used for com- 

 bining the various materials into the surface mi.Kture 

 are described with diagrams. 



.Sections v. and vi. deal with the handling of the 

 material in the street and with the hand-tools needed 

 by the workmen, and in the latter section a descrip- 

 tion of an ingenious machine for impact tests is 

 given. In section vii. there is a complete specification 

 for an asphalt pavement ; this will be found of great 

 value to engineers who have to draw up specifications 

 for work of this nature. Mr. Richardson points out 

 that the popular idea as to the limiting gradient for 

 an asphalt pavement is erroneous, and that in the 

 eastern part of the United States, for example, a 

 gradient of 8 per cent, on an asphalt road is not 

 excessive. There is no doubt that asphalt has great 

 advantages when compared with most of the other 

 pavement materials ; it is free from mud if properlv 

 washed down at regular intervals; unlike wood, it is 

 practically non-absorbent ; when kept in a clean con- 

 dition it gives a good foothold for horses; tractive 

 effort is considerably reduced, and even under heavy 

 traffic asphalt wears remarkably well, .\lthough the 

 initial cost is heavy, still the cost of upkeep is lower 

 than that for most of the other paving materials. 

 The last section of the book, one of the most valuable, 

 deals with the testing of the various materials used 

 in asphalt pavement work; it gives a complete account 

 of this necessary branch of the work, and data are 

 given of the equipment required in a municipal labor- 

 atory' where such testing work is carried out. 



The book is likely to prove of great value to 

 municipal authorities who are faced with the problem 

 of determining the most satisfactory road material to 

 employ both where traffic is heavy and where it is 

 moderate. T. H. B. 



OUR BOOK SHELF. 

 Die physikalischen Eigenschaften der Seen. By Dr. 



Otto Freiherr von und zu .'\ufsess. Pp. x+120. 



(Brunswick : Vieweg and Son, 1905.) Price 



J marks. 

 There are many books and pamphlets dealing 

 with one or several of the properties of lakes ; 

 the aim, however, of the present work is to gather 

 into a handbook the principal facts known, and to 

 give a general view of the results arrived at, so as 

 to incite the lover of nature to interesting observ- 

 ations as well as to provide a guide for "the more 

 specialised limnologist. 



In a short introduction the author deals with Prof. 

 Forel's work as having caused the important develop- 

 ment of limnology which recent years have witnessed, 

 and gives this authority's definition of a lake as being 

 " a mass of still water, closed up on all sides, situated 

 in a depression of the ground, without direct com- 

 munication with the sea." The lake surface being 

 a part of the earth surface represents a section of a 

 sphere, the curvature of the same being, with large 



