230 Transactions. — Chemistry. 



from a large nodule found in the hot baths at Wairakei. As 

 the results of analyses of the samples thus obtained would be 

 altogether on the soils formed from the acidic rocks, we felt 

 that a comparison was needed of soils resulting from basic 

 rocks, examined under the same conditions, and, as we had 

 taken pure pumice to compare with the soils arising from 

 degradation of this substance, we felt it incumbent to examine 

 samples of pure basalt under like conditions. We therefore 

 obtained from Mount Eden at different points two samples of 

 volcanic soil and the rocks in the vicinity, choosing the soils 

 from amid the rocks and boulders, which would preclude 

 the likelihood that animals had grazed in their neighbour- 

 hood. 



Having decided upon these two series of soils from the 

 acidic and basic rocks for comparison, we felt that further 

 benefit would be achieved by carrying out a similar examina- 

 tion of soil under cultivation in the Waikato district, and for 

 this we are indebted to Mr. Chapman Ewen, of Cambridge, 

 who has carefully obtained from his farm a sample to the 

 depth of 9 in., taking this from a portion which had not been 

 manured. 



Now, the mere quantitative analysis of a sample of soil, 

 giving its exact equivalent values of the various elements 

 present, however carefully done, is almost useless to the culti- 

 vator, while the amount soluble in strong hydrochloric acid in 

 a given time is almost as valueless. Until within the last few 

 years this is all that could be determined, as the conditions of 

 plant-life were not well enough known to permit of any other 

 scheme being adopted. But science has stepped forward to 

 the aid of the tiller of the land, and, in the hands of such men 

 as Voelcker, Liebig, Way, Vogel, Tollens, Stutzer, and Dyer, 

 a system has been carefully planned which has brought order 

 out of chaos. 



In a paper read before the Chemical Society by Dr. Ber- 

 nard Dyer, reported in the March number of 1894, this gentle- 

 man shows by many results that the solubility of the mineral 

 portions of the soil, in plants, is due to the acidity of the sap 

 of their roots. He estimated the acidity present in the roots 

 of about a hundred plants composed of different natural 

 orders, and found that although there is a marked difference 

 between various plants of different orders, and even in the 

 same order, still an average could be obtained over the whole 

 estimated as equal to a 1-per-cent. solution of citric acid. 

 Dr. Dyer chose citric as being an organic acid, and therefore 

 kindred to the acidity of plants. Following the reasoning of 

 this writer, othei's have used aspartic, but, seeing the accu- 

 racy and value of the work done by citric acid, we decided 

 to adhere to this solvent. 



