* BULLETIN OF THE BUSSEY INSTITUTION. 71 
It will be remembered that in the experiments where buckwheat 
was grown in coal-ashes and in pit-sand for comparison the jars con- 
tained 525 grammes of the ashes and either 1,000 (Series C) or 1,370 
grammes (Series D) of the pit-sand. The object was to fill the jars in 
each instance, and they were better filled, so far as related to pit- 
sand, in Series D than in Series C. But from the above analyses it 
appears that while each jar of the coal-ashes contained 0.26 gramme 
of phosphoric acid and 7.72 grammes of potash, the jars of pit-sand 
contained, in Series C, 0.35 gramme of phosphoric acid and 8.87 
grammes of potash, and, in Series D, 0.48 gramme of phosphoric acid 
and 12.15 grammes of potash, so that in both the series the plants 
growing in the comparatively poor pit-sand were really in presence of 
a larger amount of the fertilizing substances now in question. The 
larger mass of the sand more than compensated for the smaller pro- 
portion of potash and phosphoric acid contained in it. The question 
whether these constituents are more ‘firmly held against the action of 
plants by the pit-sand or by the ashes has therefore not been an- 
swered by the foregoing experiments. Perhaps there is no great 
difference between the two substances in this respect. In some 
points the experiments of Series C and D would seem to show that 
the matters in the sand are more readily available for the plant than 
those in the ashes; but it is hard to judge of this matter from the 
data in question, since the sand offers a certain mechanical advantage 
for the growth of plants, as has been said. Contrary to what was 
supposed at the beginning of the research, it seems, on the whole, not 
improbable that the mere analysis of the two materials indicates very 
nearly their comparative power of supplying food to plants placed in 
favorable conditions. Many other experiments upon these and upon 
analogous materials must, however, be made before the truth of this 
supposition can be accepted as proved. 
Other experiments upon the chemical composition and behavior of 
the coal-ashes and pit-sand were made as follows : — 
A five-inch glass funnel was filled with the coal-ashes and another 
with the pit-sand. Distilled water was poured little by little upon 
the materials until 100 c. ¢. of liquid: had filtered from each of the 
funnels, after their contents had become saturated with water. The 
percolates were evaporated to dryness and the residues tested by 
means of the spectroscope. No reaction but that of sodium was 
