VI 



Supplement to "Nature" November 6, 1902. 



present lecture, the fundamental importance of the con- 

 ception of heat as a form of energy was not grasped by 

 the then editor of the Annalen. It seems that at first 

 even Mayer's work was more appreciated abroad than 

 in his own country, and the great work of Joule, whose 

 first communication was published in 1843, was not 

 noticed in the Annalen until 1S48, while his second 

 memoir, published in the Philosophical Transactions in 

 1S50, was noticed in Poggendorff's Annalen only in 1854. 

 It is not surprising in these circumstances that a writer 

 who failed to enforce his views— although we now 

 know these to have been perfectly sound— -by original 

 experiments should not have succeeded in turning the 

 direction of contemporary scientific thought by two 

 philosophical essays which, bearing in mind the date of 

 their publication, were little short of revolutionary. But 

 it certainly is remarkable that his contributions should 

 have been altogether overlooked by later writers who 

 were, and are, fully cognisant of the importance of the 

 doctrines in question. Thus in the list of names given 

 by Father Secchi in 1878, that of Mohr does not appear. 

 In a lecture on the development of the exact sciences 

 during the nineteenth century given by Prof, van 't Hoff 

 before the German Association in 1900, it is pointed out 

 that the law of the conservation of energy, although essen- 

 tially a physical discovery, was not made by physicists in 

 particular. He mentions Mayer the physician, Joule the 

 brewer, Colding the engineer, and especially Helmholtz, 

 at that time a physiologist. Herr Jezler adds : — 



" Vv'arun bier nicht als erster Mohr, ein Apotheker, 

 genannt werden soil, ist mir unbegreiflich. Auf Grund 

 vorliegender Experimentalforschungen (Melloni, 1798 bis 

 1854) kam Mohr durch Induktion zur dynamischen 

 Warmelehre im Gegensatz zu der gebrauchlichen mater- 

 iellen Warmetheorie, durch Deduktion gelangte er . . . 

 /in- Einheit der Naturkrafte, gleichbedeutend mit dem 

 Prinzip der Erhaltung der Kraft." 



Cases similar to Mohr's, in which important new con- 

 ceptions have been started by men who failed to influence 

 contemporary opinions, are well known in the history of 

 science. Sometimes recognition has come during the 

 worker's lifetime, as with Newlands and the periodic law 

 —which example, by the way, is not referred to by the 

 writer of the present pamphlet, although he mentions 

 several other cases. Generally, however, the recogni- 

 tion is posthumous. As an instance of this we have 

 Waterston's anticipation of the kinetic theory of gases. 

 rescued from the archives of the Royal Society by Lord 

 Rayleigh. When by masterly and convincing treatment 

 some great generalisation which has been in the air for 

 some time previously is finally made evident to the 

 scientific world by the stroke of genius, there is always a 

 danger of reading too much into the works of the earlier 

 investigators and of interpreting their results in the light 

 of later knowledge. The writer of this notice ventures to 

 quote by way of illustration the enormously enhanced 

 reputation of Lamarck as an evolutionist since the publi- 

 cation of the "Origin of Species." Is it going loo far to 

 say that Charles Darwin has made the reputation of 

 Lamarck? In the case with which wc are immediately 

 concerned, however, a candid examination of the evi- 

 dence will, we believe, show that Herr Jezler has not 

 credited Mohr with more than was due to him. 



R. MELDI 'LA. 



N.i. 1723, VOL. 67J 



SOIL SURVEYS. 

 Field Operations of tlie Division of Soils, 1900. By 

 Milton Whitney, Chief (U.S. Department of Agricul- 

 ture). Pp. 474 + a case containing 24 maps. (Wash- 

 ington, 1901.) 

 PERHAPS one of the greatest services which the 

 scientific man can render to the agricultural com- 

 munity in any country is the classification of the soils 

 into certain types, defined by their chemical or physical 

 properties, and the allocation of these types to their 

 appropriate areas, so as to obtain a soil map of the district 

 in question. 



Despite disturbing factors, certain types of soil persist 

 over wide stretches of country and are characterised by a 

 general physical and chemical resemblance, and also by a 

 corresponding similarity in natural flora, appropriateness 

 to particular crops and responsiveness to certain kinds of 

 manure. The constancy of these soil types is the result 

 of a common origin from the same kind of rock, and the 

 difficulty lies less in recognising the type than in tracing 

 its boundary line. 



As a fundamental basis comes the geological survey, 

 particularly the "drift" maps showing the superficial 

 deposits due to running water, ice, &c, which, though of 

 no great geological importance, are the origin of the 

 soil proper. But for the purposes of a soil survey a little 

 more than even a " drift " map is wanted ; further sub- 

 divisions must be introduced to show changes in soils on 

 the same formation due to variations in the lithological 

 character of the formation, or those due to the sorting 

 action of water in the case of soils of transport. 



These variations, in fact soil classification generally, 

 must be based upon physical structure, must amplify 

 and give exactitude to the practical man's division into 

 clays, loams and sands ; the chemical properties of the 

 soil may vary concurrently, but are too much subject to 

 casual change to serve as prime means of distinction. 

 As an instance, the upper beds of the Lower Greensand 

 in east and mid Kent give rise to rich loams, on which 

 many fine hop and fruit plantations are situated ; further 

 west the formation gradually changes, until in west Surrey 

 and Hampshire it is barren heath land the soil of which 

 is alike wanting in the finer "clay" particles, carbonate 

 of lime and the soluble salts which go to feed the plant. 

 Again, in the book under notice many examples will be 

 found of two or more distinct soils of the same origin, 

 e.g. the maricopa soils (p. joj), described as consisting of 

 "colluvial materials . . . largely granite . . . divided 

 into four soils, depending upon the degree of comminution 

 of the rock.'' 



The volume before us represents a year's work of the 

 Division of Soils of the United States Department of 

 Agriculture in this particular direction of constructing a 

 senes of soil maps ; twenty-four of the maps are given on 

 a scale of 1 inch to the mile, and show, by a system of 

 colouring similar to that of a geological map, the type to 

 which the soil belongs. The accompanying text gives a 

 mechanical analysis of the type soil, i.e. its division into 

 fractions each consisting of particles of a certain size, and 

 in some cases a chemical analysis, also such information 

 collected on the spot as the distance to ground water, 

 climatic features, characteristic crops or natural flora 

 -,nd other local economic conditions. 



