On the Function of Salt in Agi'ieulture. 179 



these couclusions are drawn are a manifest corroboration of those 

 made by i\I. Reich with steel magnets. 



If we suppose the flat sm-faces of the two semicylinders which 

 constitute the ends of the cores to be in contact, and the cores 

 so excited that the poles P and P' are of different qualities, the 

 arrangement, it is evident, forms a true electro- magnet of the 

 horseshoe form ; and here the pertinency of a remark made by 

 M. Poggendorff, with his usual clearness of perception, becomes 

 manifest ; namely, that if the repulsion of diamagnetic bodies be 

 an indifferent one of the mass merely, there is no reason why 

 they should not be repelled by the centre of a magnet, as well 

 as by its ends. 



[To be continued.] 



XXI. On the Function of Salt in Agriculture. By A. Beau- 

 champ NoRTHCOTE, Esq., Senior Assistant in the Royal Col- 

 lege of Chemisti'y^. 



THE employment of salt in agriculture has been of late years 

 so much extended, that the question of the advantages 

 derived from its use, which formerly gave rise to so many discus- 

 sions, can no longer be raised. Such an accumulation of facts 

 with regard to its action has now taken place, that it is only 

 necessary to pass judgement upon the evidence recorded ; and 

 as the practical results which have been obtained by its judicious 

 application have been all more or less of a beneficial tendency, 

 the verdict given cannot fail of being in its favour. It seems to 

 be an incontrovertible fact, that the application of salt to certain 

 lands does increase their fertility, and improve the character of 

 the crops grown upon them ; and if this is the case, it is most 

 desirable that we should have as clear an idea as possible of the 

 rationale of its action. I do not in the present paper profess to 

 supply this explanation, although I hope that the experiments 

 which I am about to detail may serve to throw some light upon 

 a somewhat obscure subject. 



It has long been held that the beneficial action which salt 

 exerts upon soils is due to a power which it possesses of fixing 

 ammonia, and wita this view it has frequently been spread over 

 the surface of dung-heaps, or other organic matters decomposing 

 into manures (sometimes also being mixed up with them), with 

 the view of preventing the escape of the ammonia produced in 

 the course of eremacausis : in some cases success has attended 

 these trials, and in some, failure. The question of its absorption 



* Communicated by the Author. 



