66 BULLELIN OF iHE BUSSEY INSTITUTION. 
Series D are compared with one another, the weight of the crop ob- 
tained from the sterile Berkshire sand by the use of rain-water alone ) 
being taken as unity. 
A somewhat more satisfactory comparison between coal-ashes and 
pit-sand could probably be made by repeating the experiments in jars 
of unlike sizes, filled with equal weights of the two materials, though 
from the dissimilarity of their mechanical condition and texture it 
would not be easy to have all the conditions of the experiment pre- 
cisely similar in the two cases. No such trial has been made, for 
the reason that enough seems to have been done already to exhibit 
the two substances in their true relations. It has been proved, at all 
events, that although the ashes of the Pennsylvania white-ash coal 
examined do contain appreciable quantities of potash and phosphoric 
acid in a condition fit for the support of plants, they are, neverthe- 
less, inferior in this respect to an equal bulk of a good pit-sand from 
Eastern Massachusetts. As regards the question whether sand or 
coal-ashes is best fitted for the amelioration of low lands rich in © 
humus, it appears that it must come up afresh in every new locality ; 
it can hardly be answered at present except by means of experiments 
made upon each particular sand. 
It is true, as will be shown further on, where some results obtained 
by analyzing the two substances are contrasted, that the smaller 
weight of ashes employed in my experiments, as compared with the 
weight of the pit-sand, must be regarded as a circumstance highly 
disadvantageous to a precise appreciation of the worth of the ashes. 
It is not impossible that, weight for weight, the coal-ashes may sup- 
port better crops than the pit-sand in question. It is certain only 
that, while coal-ashes are much better in respect to fertilizing ingre- | 
dients than the really sterile sands composed wholly of quartz grains, 
they may be no better than, or even inferior to, some other common 
sands that farmers have access to. No doubt many a sand could be 
' found of precisely the same fertilizing value as pure coal-ashes. It 
must be remembered, however, that the coal-ashes actually obtained 
from house fires are almost always more valuable than those employed 
in the experiments here described, because of the admixture of wood- 
ashes to which allusion has already been made. This admixture is 
so general, and often so large, that it may well be true that coal-ashes 
of the average quality likely to be applied to the land are really better, 
