40 



INVESTIGATION INTO THE AMOUNT OF WAT EE 



such were the product for which they were usually cultivated — 

 an end not very easily accomplished in the case of plants growing 

 through a period of several months, and requiring an accurate 

 registry of the water passing through them. This was not, in- 

 deed, in every case satisfactorily attained, as will be explained 

 further on. But if from this cause any otherwise general indica- 

 tions should seem to be opposed by figures, at first sight, discre- 

 pant, a little further consideration may perhaps show that if these 

 are coincident with irregularities of growth and maturation, they 

 may be taken rather as confirmations than as contradictions of 

 any conclusions to which the results of the more naturally deve- 

 loped plants might lead us. We shall, however, submit to the 

 reader a sufficient description both of the methods of experiment- 

 ing, and of the results as they were actually obtained, whether 

 numerically or by observation merely — leaving him, |^erefore, 

 in a position to judge of the value of any suggestions we may 

 offer, whilst the experience thus far attained will, it is expected, 

 enable us to avoid in future some of the irregularities complained 

 of, and the results then supplied will serve amply to confirm or 

 correct any inferences at present hazarded. 



The plants selected for experiment were Wheat and Barley 

 of the natural order Graminacese ; with Beans and Peas as Corn- 

 plants, and Clover as a Fodder-plant, from the Leguminosae — 

 these several plants, moreover, occupying somewhat important 

 and characteristic positions in a course of rotation. A Root-crop 

 would also have been taken, but for the great and manifest diffi- 

 culties of arranging the experiment. These we hope to over- 

 come, however, in the coming season. 



The main desiderata in the arrangement of the experiments 

 were — 



To provide the plants with soils of some known history and 

 composition or resources, and in quantities sufficient to 

 allow of a natural development of the roots. 



To prevent any serious amount of evaporation from the soil 

 other than through the plants themselves. 



To have the means of supplying weighed quantities of water 

 to the soils as it was needed. 



To determine by the balance the amount of water given off 

 by the plant within any desired period of observation. 



To determine the total amount of water passed through the 

 plant during the entire period of its growth ; and in rela- 

 tion to this, the amounts of dry produce, and several of 

 its constituents fixed in the plant. 



To determine the source of these fixed constituents, whether 

 soil, manure, or atmosphere. 

 We are prepared for the objections which may be raised against 



