266 Progress in Science. (Apri, 
composition. Vom Rath’s analysis gives—Silica, 96:3; ferric oxide, 2; 
magnesia, I°1; lime, trace. There seems, therefore, no doubt that Asmanite 
is a new form of silica crystallising in the rhombic system, so that we are now 
acquainted with three species of crystallised silica, distinguished by their 
specific gravity in this wise :— 
QUIATEZ 9: Bie Lahet pie ot Sela obo gf ois) une SPU 
Dtdsyanite eveie aie) made) Bieta fodeedatt ote 5 2°3 
ASiMaTHce ete Gwe tee tls teks tele e Rete 4 2°24 
by Levy in 1824, and named in honour of Gustav Rose. It appears that only. 
two specimens are known, the one in the Werner Collection at Freiberg, in © 
Saxony, and the other in the Turner Collection in this country. Both came ~ 
from Schneeberg, in Saxony. Two new specimens, recently found at this 
locality by Herr Tréger, have been described by Prof. Weisbach. 
A continuation of Rammelsberg’s researches ‘‘On the Composition of the 
Natural Compounds of Tantalium and Niobium” has appeared in a recent 
number of ‘‘ Poggendorff’s Annalen.”’ The present portion of the investigation 
relates to the minerals called pyrochlore, yttrotantalite, fergusonite, polyclase, 
euxenite, wohlerite, samarskite, and zschynite. 7 
Prof. Zepharovich has presented to the Vienna Academy a further description 
of his new mineral, Syngenite. He now finds that the species must be 
referred to the monoclinic and not to the rhombic system; that the artificial 
salt having the same composition (namely, CaSO,+Na,50,+H20) is also 
monoclinic; and that Rumpfe’s mineral, Kaluszite, is in all probability identical 
with syngenite. 
Dr. Burkart, of Bonn, has described in Leonhard and Geinitz’s ‘**‘ Neues 
Jahrbuch” the mass of meteoric iron known as the Descubridora meteorite. 
This was found near Poblazon,in Mexico. The same mineralogist has a paper 
on the occurrence of the various minerals of tellurium and bismuth in the ~ 
United States. 
Among recently-published papers bearing as much on physics as on 
mineralogy, we may cite a memoir by Dr. Carl Klein, of Heidelberg, on the 
optical characters of the Epidote of Sulzbach; a paper by Prof. Néggerath, 
of Bonn, on the phosphorescent glow exhibited by agates and other siliceous 
stones when ground on the large wheels used in the polishing-mills at Oberstein 
} 
and Idar; and a paper by Dr. Behrens, of Kiel, on the spectrum of the precious 
opal. 
ENGINEERING—CI1VIL AND MECHANICAL. 
; 
s 
One of the rarest known mineral-species is Roselite, a substance determined { 
4 
uJ 
. 
Boilervs.—At the present day when every manufacture is carried on with the 
aid of steam, the strength of boilers is a most important question with- 
reference to the duty they are expected to perform. This, as a seétion of 
experimental science, has been very much neglected in this country. From 
- an article which appeared in the ‘‘ Nautical Magazine,’’ on the United States 
Experimental Commission, it appears that the majority of the experiments 
made by Fairbairn, on the collapsing of tubes, and upon which’a rule was 
based for the construction of steam-boilers, were with tubes of No. 19 
wire gauge, or about j,rd of an inch in thickness. According to the 
practical rule based upon these experiments, the strength against collapsing 
is directly as the square of the thickness, and inversely as the length, 
but the constant multiplier for collapsing pressure is given 71 per cent 
above the mean of the experiments, and 25 per cent above the maximum 
result obtained. Before September, 1871, Mr. Francis B. Stevens, of Hoboken, 
New Jersey, had made several experiments on the strength and proper 
management of boilers belonging to the United Railroad Companies of New 
Jersey; and so valuable did the results appear, that the Executive 
Committee of the United Companies voted 10,000 dollars for the continuance 
of the experiments, which were made on real boilers and with steam- 
power. The paper from which we quote was written before the com- 
pletion of the experiments; but, so far as they had gone, they fully indicated 
