in regard to Earthy Matters. 167 



Now, the aqueous solution represents the amount of alkali 

 combined either with the phosphoric or carbonic acids ; the solu- 

 tion in nitric acid without previous treatment, the earthy carbo- 

 nates and phosphates;* that in nitric acid, after the action of an 

 alkaline carbonate, the earthy sulphate, with that portion of the 

 phosphate which had escaped the previous action of the acid. 

 These were not distinguished with any precision one from the 

 other, because my object was merely to show that a large in- 

 crease in earthy matter had resulted from the process of vegeta- 

 tion ; but the several portions were all minutely examined for 

 strontian, of which they furnished no trace. The same year I 

 endeavoured to ascertain how much of this increase might be 

 attributable to the rain, and the matters brought with it, by the 

 following experiment : I procured six oblong boxes, of nearly 

 equal size, coated internally -with sheet-zinc, two of which were 

 filled with sulphate of strontian, two with powdered Carrara 

 marble, and two with sea-sand, well washed both with water and 

 muriatic acid. Of these, one of each kind was placed in a 

 greenhouse, where they were protected from dust and rain ; and 

 the same number in an open garden, where they were exposed 

 to both.f There was also placed in the garden a fourth box, 

 of twice the dimensions, filled only with common mould. In 

 each of the six smaller boxes were sown 780 grains of the seeds 

 of the winged-pea trefoil (Lotus tetragonolobus) ; in the largest 

 one double that quantity ; and when the plants had severally 

 grown up in their respective situations, they were cut down, 

 dried, reduced to ashes, and examined, a comparative analysis 

 being at the same time made of a quantity of the seeds equal 

 to that planted in each of the six smaller boxes. It will be seen 

 from the following tabular view of the results obtained, that in 

 every one of these cases there was an excess of earthy salt be- 

 yond that existing in the seeds, and in one case an excess of al- 

 kaline ; those even which had vegetated in a soil chiefly consist- 

 ing of sulphate of strontian obtaining, nevertheless, an increase 

 of earthy matter, and this containing not even a trace of stron- 



* The difference in the quantity of lime to be inferred from 100 of phos- 

 phate and 100 of carbonate was only as 53 to 56. 



+ I am indebted to Professor Buckland for the use of a garden, in which 

 the boxes were placed during the time the experiment lasted. 



