58 FF. H. Storer—Shell- and Rock-boring Mollusks. 
of mercury. Le Sage, a writer of the last.century, 1777, also 
mentions prismatic crystals of gold obtained by heating the 
amalgam. He describes them as square prisms with terminal 
pyramids of four planes, and considered them to be lengthened 
octahedrons. 
Mill Rock, New Haven, June, 1884. 
Arr, XI.—WMode of action of Shell- and Rock-boring Mollusks ; by 
Professor Ff. H. Storer. (Letter addressed to J. D. Dana.) 
- ? 
the true explanation of the mode of action of many rock- and 
nown as water-culture, which has played a highly important 
part in the study of the question what chemical substances are 
necessary for feeding plants. Knopt found, for example, on 
growing maize plants in solutions containing the nitrates of 
lime and potash that the nitrogen of these compounds was 
s 
alkaline through accumulation of the bicarbonates of potash 
and of lime. So, too, when Rautenberg and Kiihn tried to sup- 
. * This Journal, July, 1878, III, vol. xvi, 32. 
t See his “ Lehrbuch der Agricultur-Chemie,” i, 603. 
