131 
like siliceous skeletons are very durable. Diatoms are often so 
numerous in both fresh and brackish waters that the flinty shells 
left on their death form large deposits. Extensive deposits 
of diatomaceous matter are found in sedimentary rocks of various 
geological ages, especially from the Tertiary onward. These 
diatomaceous earths are put to various economic uses, the prin- 
cipal being as ingredients of scouring compounds or polishing 
powders, as a matrix for absorbing the gum in the manufacture 
of rubber goods, and also, it is said, as a matrix or carrier in the 
making of dynamite. Two of the best-known quarries of dia- 
tomaceous earths in the United States are at Richmond, Virginia, 
and in Nevada. 
The Horticultural Society of New York, in codperation with 
the Garden, will hold its summer exhibition of plants and flowers 
in the Museum Building. The exhibition will open on Saturday 
afternoon, June 4th, at 2, and will close at 6, and will remain 
open on the following day, from 10 to 5. Premiums have been 
offered by the Garden, to be awarded through the Council of the 
Horticultural Society, for peonies, roses, flowering shrubs and 
trees, orchids, and irises and other hardy herbaceous plants. An 
invitation is extended to all to enter exhibits, whether members 
of the Horticultural Society or not. 
Following the meeting of the Horticultural Society on Satur- 
day afternoon, there will be a public lecture, in the lecture- hall 
trated with colored lantern-slides. At the close of the lecture, 
about 5 o’clock, opportunity will be eee for visiting the 
grounds of the Garden under guidan 
Meteorology for April_—The eh etion recorded for 
the month was 4.39 inches. Maximum temperatures were re- 
corded of 78.5” on the 5th, 80° on the 15th, and 79.5” on the 30th; 
also minimum temperatures were recorded of 35° on the 8th, 
29.5° on the 13th and 35° on the 2gth. 
