366 BULLETIN OF THE BUSSEY INSTITUTION. 
more abundant use which these salts will find in British agriculture. 
. . It follows clearly from the results of the experiments on pota- 
toes here recorded, and of those previously published by me, that 
potash-salts materially increase the produce of potatoes, and that 
they are very useful constituents in a potato-manure — at all events 
upon light land.” 
More than a century ago Home,* of Edinburgh, observed that 
the application of sulphate of potash had. a beneficial effect on 
vegetation, and Sprengel, in his day, reported similar experiences 
from Germany ; but the salt was then too costly to permit its com- 
ing into use as a manure. 
In vol. I. p. 386 of this Bulletin I have already alluded to the 
use at Sandwich in this State, between the years 1820 and 1840, 
of sulphate of potash, such as is obtained in the refining of pearl- 
ash for glassmakers.t It was found to give excellent results when 
applied admixed with loam as a top-dressing to grass, rye, corn, 
and oats. In this case it might be argued, with some show of jus- 
tice, that the presence of a small proportion of carbonate of potash 
that remained clinging to the sulphate may have increased the fer- 
tilizing effect of the material. Perhaps it might be worth the while 
in some localities to try field-experiments with chloride of potas- 
sium (or with the sulphate) with which carbonate of potash (pot- 
ashes) had been mixed in various proportions, in order to test the 
merit of such admixture in comparison with the mixtures of lime 
and potash-salts which have been a good deal used abroad. It 
would undoubtedly be well also to experiment with artificial ashes, 
i. e. with mixtures of carbonate of potash and of lime that has been 
slacked with water and afterward carbonated by exposure to the 
air, with the view of finding which among several potassic ferti- 
lizers may be best fitted for a given field or farm. 
Pure sulphate of potash, such as is made for medicinal purposes, 
has sometimes been used in this country, to my knowledge, in con- 
junction with nitrogenous and phosphatic fertilizers, for manuring 
tobacco. The motive in using the comparatively costly refined 
product was to avoid any contamination with chlorides, which are 
known to injure the combustibility of the tobacco leaf. 
The general impression that sulphate of potash is a better ferti- 
lizer than chloride of potassium seems on the whole to be founded 
* Cited by J. F. W. Johnston, in his ‘‘Lectures.on the Application of 
Chemistry to Agriculture,’ New York, p. 330. 
+ ‘*Colman’s Fourth Report of the Agriculture of Massachusetts,” p. 344. 
