38 REPORT— 1842. 



amined, to contain as large a quantity of phosphate of lime as that mentioned. 

 Though the soil of Great Britain be found deficient in the phosphates, there is reason 

 to believe the subsoil might in many cases be made, by proper management, to im- 

 part to it what was wanting. The discovery by Dr. Buckland, in the lias and 

 other secondary rocks, of the solid faxes of certain extinct animals, consisting of 

 phosphate of lime, induced Dr. Daubeny, some years since, to test a variety of 

 specimens of limestone, with a view of ascertaining whether traces might be found 

 in them of the same ingredient. The result was, that phosphate of lime in minute 

 quantities was much too commonly distributed to be attributed to coprolitic matter, 

 or to afford any independent evidence of its presence. When, indeed, we recollect 

 that the shells of invertebral animals contain from three to six per cent, of phosphate 

 of lime, and that, according to Mr. Connel, the scales of extinct fish, taken from 

 xocks as old as the coal formation, possess no less than fifty per cent, of the same 

 ingredient, it would be wonderful, indeed, if all traces of this substance had disap- 

 peared from rocks which appear often to be made up in a great degree of the debris' 

 of shells and other marine exuviae. Dr. Daubeny was, therefore, not surprised at 

 being informed by M. Schweitzer, who is intrusted with the management of the 

 German Spa at Brighton, that he had detected in the chalk of Brighton Downs, 

 as much as TWSE^ 1 part of phosphate of lime. From experiments since made 

 by Dr. Daubeny on the same rock, taken from various localities, he was inclined to 

 believe, that minute portions of this substance are present not uncommonly in that 

 formation. The frequent occurrence of phosphate of lime in calcareous rocks, and 

 the probability of its having been derived from the shells or bony matter of the living 

 beings contained in the calcareous rock, led Dr. Daubeny to suspect that traces also 

 of the organic matter which contributed to make up the animal structure, might 

 likewise be found accompanying it. He had accordingly availed himself in several 

 instances of the property which a solution of nitrate of silver possesses of becoming 

 black, by being brought into contact with organic matter on exposure to the light, 

 as a ready means of ascertaining the presence of organic matter in a specimen of 

 limestone ; and whilst by this test he determined its entire absence from Carrara 

 marble, chalk from the neighbourhood of a basaltic dyke on the coast of Antrim, and 

 even in many instances from petrifactions of shells contained in the secondary rocks, 

 he had obtained indications of the presence of some form of organized matter in se- 

 veral of the tertiary rocks, and even in the chalk. 



This test, however, cannot be successfully applied, except when bituminous matter 

 and every other form of mineral carbon are absent, and when the non-existence of 

 common salt has been previously established by the absence of any cloudiness upon 

 the addition of nitrate of silver after an exposure to light has taken place* ; nor 

 does this test enable us to determine whether the organic matter is of a vegetable or 

 an animal nature ; to ascertain the latter, a modification of Will and Varrentrapp's 

 process for estimating the amount of nitrogen in organic matter might probably be 

 adopted, the insoluble portion being heated with quicklime and caustic alkali in an 

 iron or platina tube, and the vapours being collected in a receiver containing muriatic 

 acid, or tested with turmeric paper. 



Dr. Daubeny read a letter from M. Schweitzer, who states that he had been pre- 

 cluded from employing the secondary limestones in obtaining carbonic acid where- 

 with to impregnate his mineral waters, owing to an empyreumatical odour which the 

 gas carried up, and which he attributed to an organic cause. To obtain a perfectly 

 pure carbonic acid, for his imitation of the spas of the continent, he was compelled 

 to resort to the white kinds of marble. With regard to the presence of organic 

 matter in the subsoil, its detection may be a matter of some agricultural interest, 

 when we remember that the small quantities of nitrogen which are required for the 

 growth of those vegetables that first start up in a new country, could not have 

 been derived from an accumulation of mould by the decay of antecedent plants, but 

 must have arisen in a great measure from the animal matter, which is contained in 

 the rock upon which they grew, and which proceeds from the exuvije of races of 

 beings belonging to a former period of creation. In a more advanced stage of vege- 

 tation, this same material may be of some value to the crops that occupy the soil. 



* Common salt is present generally in chalk from the neighbourhood of the sea, and some- 

 times even in sueciuieus from the iuterio;'. 



