January 25, 19 12] 



NATURE 



429 



where race has overrun race and culture succeeded culture, 

 archaeology is not self-sufficient, but it may often point 

 the way to further research. For instance, at Ixkum, in 

 northern Guatemala, a stone relief shows two typical 

 Maya standing on two individuals of a totally different 

 type. The latter probably represent a conquered race. 

 Near the city of Guatemala stone figures have been dis- 

 covered closely resembling this non-Maya people. Ruins 

 in the neighbourhood bear an interesting resemblance in 

 plan to those at the famous site of Teotihuacan in Mexico, 

 but the site still awaits proper investigation. 



Another point from which the antiquity of American 

 culture may be argued is the distinctive nature of American 

 art ; but while general similarities exist all over Central 

 and South America, local developments occur, e.g. at 

 Mitla, which are not only 5Mt generis, but are, apparently, 

 accompanied by no remains which indicate how they were 

 evolved. Certain motives appear to be almost universal, 

 such as the serpent, and the quetzal-h'wA, which occur in 

 various combinations, and also the water-plant, which is 

 interesting as being the only vegetable form in American 

 art. A few instances such as these show what a vast field 

 for investigation is offered by America, the study of which 

 has been rather neglected in this country. This year, in 

 .May, we shall be welcoming the International Congress 

 of .Americanists to London, and though we possess in 

 England more pre-Columbian objects of interest than any 

 other European country, it is the first time that we have 

 acted as hosts to the leaders of American research. 



THE USE OF PHOSPHATIC FERTILISERS IN 

 FRANCE. 



CO.ME years ago M. Risler took an inventory of the soils 

 "^ of France, classing them as complete if they contained 

 suflRcient food material to yield fair crops, and incomplete 

 if they were markedly deficient in any particular food con- 

 stituent. Out of a total agricultural area of 49,000,000 

 hectares, no fewer than 36,000,000 were deficient in phos- 

 phates, and could not be made to yield profitable crops 

 without liberal dressings of phosphatic fertilisers — a state 

 of affairs that was not the result of previous bad cropping, 

 but of lack of phosphorus in the original rock material. 



In order to make good this deficiency, French agri- 

 culturists use both basic slag and superphosphates, but very 

 little of the rock phosphates so popular in America. More 

 than a quarter of a million tons of basic slag are used 

 annually on the grass land, especially where the soil is 

 derived from granite and schists, while about one and a 

 half million tons of superphosphate are used annually on 

 the arable land, and a good deal of phosphate is also con- 

 tained in the guano applied as fertiliser. 



But, vast as these quantities are, they are insufficient, 

 and consequently there has been a marked increase in the 

 price of phosphatic fertilisers during recent years. The 

 various factors coming into play have been recently analysed 

 in an article by M. Hitier in the Bulletin de la Soci4U 

 d' Encouragement pour I'lndiistrie Nationale (No. 6, 

 vol. cxv.). 



Superphosphate, as is well known, is made by treating 

 rock phosphate — an impure tri-calcic phosphate — with 

 sulphuric acid, and in order to overcome transport and 

 other difficulties, the sulphuric acid is usually made on the 

 spot at the factory itself. Both the raw phosphate and 

 the pyrites from which the sulphuric acid is made have 

 increased in price; the world's consumption of phosphates, 

 which was four and a half million tons in 189.S, had in 

 iqo8 increased to ten million tons. The price of super- 

 phosphates in France has usually been lower than in 

 P-ngland, but now that the French deposits of rock phos- 

 phate are giving out, it has been necessary to look else- 

 where. At present nearly half of the world's supply comes 

 from North .America, North .Africa, however, also furnish- 

 ing a great deal. Other supplies come from the Pacific 

 Islands and the north of France and Belgium. 



Investigations have shown that dressings of phosphates 

 not only raise the quantity of the crop, but also improve 

 the quality. Miintz showed that dairy produce, particu- 

 larly butter, of the finest quality was obtained only from 

 pastures exceptionally rich in phosphates. More recently 

 M. Paturel has traced a clear connection between the 



NO. 2204, VOL. 88] 



quality of wine and the supply of phosphates. Analyses 

 of numerous samples during the last ten years show that 

 the best wines are richest in phosphoric acid, of which 

 they contain about 03 gram per litre, whilst the second. 

 third, and fourth classes are successively poorer. Further 

 if the vintages for different seasons are arranged in ord' i 

 of their phosphoric acid content, the list thus obtained is 

 almost identical with the order of merit assigned by the 

 wine merchants. 



THE CARBONISATION OF COAL.' 

 II. 

 T-TAVING gained an idea of the results desired in the 

 manufacture of illuminating gas and furnace coke, 

 we can pass on to the thermal conditions existing during, 

 carbonisation, and at the outset we are met by the 

 difficulty that little is known as to the heat of formation 

 of coal, and that a variety of opinions exists on this point. 



It is evident that, as the composition of coal in a mine 

 will vary not only in different seams, but even in the 

 same seam, there is no definite composition, and that 

 nothing can be known as to the heat of formation except 

 by direct determination, which necessitates experimental 

 estimations of so complicated a character' that the intro- 

 duction of errors is extremely likely to vitiate the results. 



Probably the most valuable work done in this direction 

 is to be found in a report presented by M. Euchene on 

 the thermic reactions which occur during the distillation 

 of coal, which is in the Transactions of the International 

 Gas Congress in Paris, 1900, in which he determines the 

 thermo-chemical data coming into play during the dis- 

 tillation of coal in the manufacture of gas, with careful 

 estimations of the heat of formation of the products of 

 the distillation as compared with the heat developed by 

 the fuel needed for the distillation ; that is to say, a 

 balance is struck, showing on the one side the heat 

 generated, and on the other the heat expended, the differ- 

 ence found representing the heat of the decomposition 

 of coal. 



Mahler also determined the calorific value of a coal 

 and of the products obtained on carbonising it, and both 

 these observers found that the calorific value of the coal 

 exceeded that of the products — that is, that coal is endo- 

 thermic, and that its decomposition evolves heat — but it 

 is quite clear that in the determination of a factor of this 

 kind, which is dependent upon the difference between two 

 figures obtained from a highly complicated set of deter- 

 minations, each with its own source of error, and all 

 tending in the same direction, these will be borne by 

 the resultant, and it is not surprising, therefore, to find 

 that with a coal of the same type Mahler found the heat 

 of decomposition to be -|- 25483 calories, whilst Euchdno 

 found it to be 4-63-51 calories. 



In Mahler's work the result was arrived at by deducting 

 the heat of combustion of the products from the heat of 

 combustion of the coal, whilst Euch6ne's determinations 

 were obtained by taking the difference between the heat 

 supplied and the heat consumed during distillation, so 

 that the difference between the two would be likely to 

 be increased by errors leading in opposite directions. 



M. Euch6ne has determined in this way the heat liber- 

 ated during the distillation of three types of coal, these 

 results showing in a striking way that the heat liberated 

 increases in nearly regular ratio with the amount of 

 volatile matter in the coal, and that the more oxygen 

 the coal contains, the more endothermic its reaction, a 

 fact which points clearly to its being the oxygen-bearing; 

 compounds in the coal which give it its endothermic 

 character. 



It seems likely that when the oxygen in the coal falls 

 below 3 per ceiit., all endothermicity will disappear, or 

 at any rate become negligible, whilst with gas coaJs of 

 the type most used in England, containing about 3a per 

 cent, of volatile matter and 7 to 8 per cent, of oxygen, 

 it will approximate to 250 calorics or 450 B.Th.U. per 

 pound of coal, but all Ihe evidence ns to this property in 

 coal is of an unsatisfactory character. 



When a coal is carbonised, it decomposes into gases 



1 From a course of Cantor leciiire<i given *t the Royal Society of Art< in 

 November and December, 1911, by Prof. Vivi.in B. Lewes. Continued from 

 p. 368- 



