316 report— 1879. 



assumed by some that some plants assimilated the free nitrogen of the atmo- 

 sphere ; but the authors considered that the balance of the direct experimental 

 evidence on the point was decidedly against such a supposition ; and so far as their 

 existing evidence went they considered it much more probable that the different 

 plants only took up combined nitrogen, and chiefly from the soil. They showed 

 by reference to their experiments that in the growth of wheat or barley for many 

 years in succession on the same land without nitrogenous manure the annual yield 

 of nitrogen in the crop gradually diminished. With this they found a diminution 

 in the percentage of nitrogen in the soil. In the case of the root crops, where the 

 diminution in the annual yield of nitrogen was even greater than in the case of the 

 cereals, the diminution in the percentage of the nitrogen in the soil was also greater. 

 In the case of beans there was also a diminution in the yield of nitrogen in the 

 crop, but still much more was yielded over the later period than in either wheat 

 or barley. In this case there was not found a marked reduction of nitrogen in 

 the surface soil. In the case of the mixed herbage experiments very much more 

 nitrogen was yielded by the application of potass manure ; and here they found a 

 great reduction in the percentage of nitrogen in the soil. In the case of clover 

 grown for many years in garden soil, the percentage of nitrogen in the soil was 

 also very largely reduced. Part of this reduction might be due to other causes ; 

 but the indication was that the leguminosae had derived their nitrogen from the 

 soil. Admitting that the sources of the whole of the nitrogen of vegetation were 

 not conclusively made out, they nevertheless considered that the existing evidence 

 was against the idea of the assimilation of free nitrogen by plants, and in favour of 

 the opinion that the nitrogen was mainly, if not entirely, derived through the 

 medium of the soil. 



2. The Bare Metals of the Yttrium Group. 

 By T. S. Humpidge, Ph.D., B.Sc. {Bond.) 



This paper consisted of a few remarks on some experiments with these metals, 

 instigated for the purpose of finding some better method of separation of the metals, 

 and of separating the metals themselves to determine their specific heats. The 

 main objects of the investigation produced only negative results. 



The material employed for the preparation of the earth was gadolinite, and the 

 method of extraction was the usual one. The earths themselves were separated by 

 Bunsen's well-known method with the basic nitrates ; no better means of separa- 

 tion could be found. Three earths were first obtained, viz., yttria, terbia, and 

 erbia, with their usual properties. Afterwards Marignac's ' ytterbia ' was looked 

 for in the supposed pure erbia, and the existence of this new earth confirmed. The 

 earths ' X ' of Soret, ' phillipia,' and ' decipia ' of Delafontaine in all probability do 

 not exist ; though at present the evidence at our disposal is too meagre for any de- 

 cisive opinion to be formed. 



The reduction of the fused chlorides by an electric current was attempted, but 

 numerous experiments only yielded the metals in the shape of a powder of small 

 metallic scales; their specific heats could not therefore be determined. As no 

 volatile compound of these metals is known, the only other method for determining 

 their atomic weights was by isomorphism. Rammelsberg had stated several years 

 ago that the sulphates of cadmium, didymium, and yttrium are isomorphous, whence 

 he drew the inference that the two latter metals (or groups of metals) are dyads, 

 and their oxides therefore monoxides. This was proved to be incorrect by Hilde- 

 brandt's experiments with the didymium group of metals, by which he found that 

 their specific heats were such that the atomic weights assigned to them by 

 Eammelsberg must be increased by half as much again, so that their oxides would 

 become sesquioxides. Kopp has lately shown, and his experiments have been con- 

 firmed by the author, that the isomorphism which Rammelsberg imagined to exist 

 between the cadmium, didymium, and yttrium salts is forced and unnatural, and, 

 further, that cadmium sulphate and didymium sulphate, or cadmium sulphate and 

 yttrium sidphate do not crystallise regularly together ; while, on the other hand, 

 didymium sulphate and yttrium sulphate do so. Yttrium and the other metals of 



