42 The American Naturalist. asia : 
glad to know that it is on sale by the Philosophical Society of 
Washington, from whose secretary it may be purchased for $1. 
The Novaculites of Arkansas.—In his excellent discussion of 
the novaculites of Arkansas, Griswold* describes most of these rocks a8 
consisting of very tiny irregular grains of quartz with occasional — 
specks of carbonaceous matter. Originally the rock contained also 
wel) crystallized rhombohedra of calcite, traces of which are sometimes q 
seen in the sections. Generally, however, the calcite has entirely 
disappeared, and its place is now occupied by a rhombic cavity, around 
which the quartz grains are packed as though they had been shoved — 
about by the crystallizing carbonate. The good cutting qualities of 
Arkansas whetstones are thought to be due to the presence of these — 
cavities. The purity of the Hot Springs novaculite is shown by an 
analysis that yielded : 
ent ars sie & 
Bias Sond ae MGA > oe Mah ae A ges N 
SiO, ALO, aiit be MgO K,O Na,O Loss Total 
99.45 2 tr. 19 64 e .06—100.62 
According to the author the rocks were first deposited as a mud or — 
ooze, in which calcite crystallized. They were then consolidated by — 
simple pressure, and finally, after upturning and erosion, they weré : 
supplied with a small quantity of secondary silica. i 
Petrographical News.—Osann’ has discovered that the mineral — 
heretofore regarded as sodalite in the Montreal eleolite-syenite is 
nosean, as it contains 5-6% of SO,, and very little calcium. It is quite 4 
abundant in the rock, and is Kaea as idiomorphic grains in its : 
garnets. A microscopical test proposed by the author for distinguish- a 
ing between nosean and sodalite is as follows: Moisten slide with . 
dilute acetic acid to which a little barium-chloride has been added, and ig 
allow to stand in an atmosphere of the acid. Sodalite remains trans- 2 
parent, while nosean is covered with an opaque coating of barium — 
sulphate. a 
The coloring matter of the black limestone of the Pyrenees is show? — 
by Jannetaz* to be carbon, probably in the form of anthracite. 
The new catalogue of geology and petrography issued by Ward's 2 
Natural Science Establishment, of Rochester, N. Y., deserves mention — 
*Ann. Rep. Geol. Survey of Ark. for 1890, Vol. iii, pp. 122-168. 
‘Neues Jahrb. f. Min., etc., 1892, i, p. 222. 
*Bull. Soc. Franç d. Min., xv, 1892, p.'101. 
