MANURES. 89 



informed that guano and ammoniacal manures do not seem to do 

 much good on this soil, while the application of niter is followed 

 with marked effect. 



The most decided change in the composition of this liquid is 

 observable in the proportion of potash which is contained in the 

 filtered liquid ; for, as in the case of the former soil, a considerable 

 quantity of this alkali has been absorbed by the sandy soil. On 

 the other hand, there is only a trifling amount less chloride of 

 sodium in the liquid after than before filtration, thus affording 

 another proof that the power of soils to absorb potash is much 

 greater than to retain soda. It will likewise be observed that, 

 instead of yielding carbonate of lime to the liquid which was 

 brought into contact with the light soil, some carbonate of lime 

 and all the sulphate of lime were actually retained. This soil, it 

 will be remembered, is deficient in lime. Perhaps it may not even 

 contain suflBcient to supply the wants of some crops, and seems to 

 be endowed with the property of absorbing lime from manuring 

 matters, affording thereby an interesting instance how special 

 provision is made in soils for the absorption of those constituents 

 which are naturally deficient in them, an«l which are required in 

 considerable quantities for the healthy and luxuriant growth of 

 our crops. 



In the preceding experiment, just the opposite took place ; for it 

 will be remembered that the drainings, after passing through the 

 calcareous clay soil, contained a great deal more of lime than before 

 filtration. Similar differences will bQ observed with respect to 

 other constituents originally present in the liquid, and retained in 

 the stiff and in the sandy soil in very different proportions. I 

 abstain from noticing any minor changes in the composition of the 

 filtered liquid, nor shall I indulge in any speculations respecting 

 the compounds in the soil which have contributed to these changes 

 and the new combinations in the soil which may have resulted 

 from them. Our present knowledge on the subject is far too im- 

 perfect to warrant us to theorize profitably on these matters ; I 

 therefore prefer to send forth for the present my analytical results 

 without any further comment, and conclude by expressing the hope 

 that I may be permitted to continue similar inquiries into the 

 physiology of soils, and do not doubt that great and important 

 practical benefits will, in due course, be derived from increased 

 knowledge of the properties of soils and the changes manuring 

 matters undergo when in contact with them. 



