522 Progress in Science. (October, 
an improved kind of emery has led to the discovery of many new localities of 
corundum in this region. Some of these localities have been described by 
Prof. C. U. Shepard. The corundum seems to be found across a stretch of 
country at least 170 miles long and about to miles broad; but it is likely that 
this zone will be yet much extended. Throughout this region gneiss is the 
prevailing rock, but the corundum occurs directly in a chrysolitic rock, re- 
sembling serpentine. 
Some crystallographic studies of the beautiful specimens of Datulite, well 
known from the Bergen Hill Tunnel, in New Jersey, have been described in 
‘*Silliman’s Journal’’ by Mr. E.S. Dana. Upwards of 200 specimens have 
been carefully examined ; four distinct types are recognised, and many new 
forms are described. 
Mr. T. D. Rand has described some pseudomorphs of serpentine in form of 
staurolite, from the neighbourhood of the soapstone quarry, on the north-east 
bank of the Schuylkill, between Philadelphia and Montgomery counties. 
Six-rayed stellate forms of serpentine have been found, identical in shape 
with crystals of staurolite. Mr. Rand also describes the species Hisingerite 
from the Gap Mine, Lancaster Co., Pennsylvania ; and an alkaline incrustation, 
consisting chiefly of sulphate of soda, from some decomposed mica-schists 
cut through on the new line of the Philadelphia, Wilmington, and Baltimore 
Railroad. 
An analvsis of the mica from the granite of the Adamello group, south of 
the Ortler, in Tyrol, has been published by M. A. Baltzer. From this analysis 
it appears to be an iron-magnesia mica allied to Soltmann’s lepidomelane and 
to Scheerer’s mica, from the Norwegian zircon-syenite. The Adamello 
granite was regarded by Zirkel as a diorite, and by Vom Rath as a distin& 
species of rock, whilst according to Baltzer, it is merely a variety of granite. 
The same authority has examined the Blegi volite from Glarnisch, in the 
Canton Glarns. This is an oolitic iron-ore, evidently deposited from the old 
Jura sea. Treated with water, it yields a solution containing many of the 
constituents of sea-water. The saline matter must have been derived from 
the sea-water included in the mass at the time of its deposition. 
Dr. Carl Klein, of Heidelberg, has published in Leonard and Geinitz’s Neues 
Fahrbuch, the results of his crystallographic studies on the epidote and 
apatite of the Sulzbachthal in the Pinzgau. 
Extensive deposits of Cryptomorphite are said to have been recently found 
in Nevada. The mineral occurs in large nodules, and is described as having, 
in many cases, the appearance of French chalk. 
ENGINEERING—CIVIL AND MECHANICAL. 
Guns and Armour.—On the 5th of last July an important experiment was 
made with our present system of guns and armour for our ironclads by an 
attack upon the turret of the armour-clad steamer Glatton by one of the 
25-ton guns fired from the Hotspur. The result of this contest proved that 
up to the present the art of defence is in advance of that of attack, inasmuch 
as the vessel attacked came out of the contest free from any material injury. 
In this respect the present experiment corresponds in its results very much 
with those obtained by the trials which took place in 1866, when the armour 
of the Royal Sovereign was attacked by the g-inch 12}-ton gun of the 
Bellerophon, and with the results of the experiment made in 1861 against the 
cupola gun shield of Captain Coles on board the Trusty. In each case 
the heaviest available artillery was brought to bear against the shield, and in 
each case the defence proved superior to the attacking force. So far, then, it 
may be inferred that our present system of armour-plating is sufficient pro- 
tection against the heaviest artillery that can be brought against it; to what 
extent it would prove effective against the enormous masses of iron which 
low pressure guns upon Mr. Bessemer’s process might hurl upon it is a question 
which may perhaps be safely deferred until that system has been adopted. 
