226 ANNUAL OF SCIENTIFIC DISCOVERY. 



sesquioxide, crystallized in spangles, as has been for a long time 

 established in calcining sulphate of iron with chloride of sodium. 



The same process thus furnishes both silicates and phosphates in 

 the dry state without excess of acid, which readily yield to plants not 

 only silica and phosphoric acid, but also a considerable quantity of 

 alkali. Comptes Rcndus, Chem. News. 



LIME IX AGRICULTURE. 



In a paper lately read by Boussingault before the Paris Academy 

 of Sciences, he stated that lime introduced in an arable soil very 

 quickly sets at liberty a certain quantity of azote in the state of am- 

 monia. The elements of the ammonia were before united in insolu- 

 ble combinations not assimilable by plants, but the action of the lime 

 sets them free, and thus permits a part of the capital buried in the 

 soil to be utilized for the next crop. Boussiugault thinks that cer- 

 tain mineral matters, such as potash and silica, may be liberated in 

 the soil by the lime ; that other substances injurious to plants are 

 destroyed or modified by the same agent, and that to these effects is 

 added besides a physical action, changing the constitution of the land. 

 The action of lime is thus excessively complex, and its good effects 

 can only be explained by studying attentively the special circumstan- 

 ces under which they are produced. 



PRESENCE OF PHOSPHORIC ACID IX THE IGXEOUS ROCKS. 



BY JAMES SCHIEL. 



Descending from the Sierra Nevada into the plains of the Sacra- 

 mento River, by the route which leads along Black Bute, we meet, 

 west of the Bute, with a phosphoritic trachyte crumbling into pieces 

 and covering the surface for many miles. As there is hardly a trace 

 of organic substance to be discovered in the soil from which a luxu- 

 riant vegetation is springing, it was to be expected that the rock 

 contained phosphoric acid. 1 This an analysis showed to be the case. 

 The phosphoric acid is contained in the precipitate obtained by am- 

 monia after a pulverized portion of the rock has been disintegrated 

 by fluohydric acid, heated and dissolved in chlorhydric acid. The 

 washed precipitate is dissolved in a small quantity of hot chlorhydric 

 acid, much tartaric acid and some sulphate of magnesia added, and 

 then the phosphoric acid precipitated with an excess of ammonia ; the 

 crystals of the phosphate are formed immediately. The amount of 

 phosphoric acid contained in the rock was thus found to be 0.26 per 

 cent., corresponding to 0.78 per cent, of phosphate of lime. Siili- 

 man's Journal. 



SOME POINTS IN CONNECTION WITH THE EXHAUSTION OF 



SOILS. 



The following is an abstract of a paper on the above subject read 

 at the meeting of the British Association, 1861, by Messrs. Lawes 

 and Gilbert, the well-known agriculturists : 



1 Fownes ( Prize Essay, 1845) demonstrated the general presence of phosphoric 

 acid in crystalline rocks. ED. 



