502 
Lassen’s Peak is composed of dacite. This rock 
Richthofen considered to be typical nevadite, but Mr. 
Diller’s investigations confirm Mr. Iddings’s view that 
it is dacite. Gray dacite is abundant about the south- 
ern base of the mountain, in smooth cliffs and ledges, 
and has a remarkably gneissic appearance. Red da- 
cite forms the summit of the peak, and a large por- 
tion of the northern rim. 
Basalt has, perhaps, the widest distribution of all 
the rocks found in the vicinity of Lassen’s Peak, and 
itis, as arule, the most recent of the flows. An-older 
basalt has been found in the stratified tufa, which 
forms great belts along the western base of the moun- 
tain. Between Red Bluff and Mill-Creek valley, south 
of Lassen’s Peak, a distance of forty-five miles, 
wherever the surface is not occupied by tufaceous 
deposits, the rocks are basaltic. Lassen’s Peak is an 
ancient voleano, and has poured out a great variety 
of lavas which are arranged in a most favorable posi- 
tion for a study of their succession. 
Rocks of Mount Shasta and vicinity. — During a 
part of February, Mr. Diller was busy with the mi- 
croscopic study of the metamorphic and eruptive 
rocks collected by him last season, along the Sacra- 
SCIENCE. 
‘on Mount Shasta. 
[Vor. IIL, No. 
mento River north of the mouth of Pit Rivers and 
The metamorphi¢ rocks referred — 
to consist mainly of augitic gneisses; and the erup- 
_ tive rocks of the same region are, in part, gabbros. 
Some of the latter present peculiarities that cannot be 
positively determined until some chemical examina- 
tions have been made. The specimens have there- 
fore been submitted to Professor Clarke for chemical 
analysis. 
Mr. Diller has examined some thirty thin sections 
of rocks from Mount Shasta, and finds that they are 
divisible into three groups; viz., hornblende ande- 
site, hypersthene andesite, and basalt. The rocks of 
Shasta are quite similar to those of Lassen’s Peak, 
with the exception that the basalts of the former are 
much richer in olivine, and contain less globulitic 
base. 
Crater Mountain (or Shastina), on the north-west 
spur of Mount Shasta, is composed of hornblende 
andesite; and through this, on the western slope, 
there has burst a large stream of hypersthene ande- 
site which stretches far to the westward, towards 
Sissen’s ranch, in Strawberry valley, on the Sacra- 
mento. 
RECENT PROCEEDINGS OF SCIENTIFIC SOCIETIES. 
Engineers’ club, Philadelphia. 
April 19. —Mr.8S. N. Stewart described a cushioned 
pier and rolling trunnion drawbridge. With a work- 
ing model, he showed that a six-pound draw could be 
turned by a pennyweight pressure or a breath, and 
claimed, that, with a leverage six times as great as 
that of the model, twenty pounds pressure would 
turn a hundred-ton draw. Mr. William P. Osler 
presented, for Mr. J. Godolphin Osborne, an account 
of the Pocahontas mine disaster. He showed how 
probable it was that gas would have been detected 
by the engineers had it existed, and explained the 
method of damming and flooding the mine with 17,- 
500,000 gallons of water to extinguish it; the latter 
being accomplished in sixteen days, one day being 
lost in repair of adam. ‘The cause of the explosion 
is, as yet, unknown. Mr. E. 8S. Hutchinson sup- 
plemented the above by an account of his recent visit 
to the mine, confirming, as far as he had observed, Mr. 
Osborne’s opinion of damage to the mine. Timbers 
were displaced, cars demolished, etc.; but there was 
no fall of roof, except in the fan-entry, where much 
slate had fallen, but where a week’s work would 
repair damage. He attributed the safety of the roof 
to the fact that from 12” to 18” of coal had been left 
as an elastic support to the treacherous slate above. 
He considered the presence of five or six inches of 
fine, dry coal-dust on the floor a phenomenon of 
special interest, and, while withholding a positive 
opinion in view of pending investigations by a com- 
mittee of the American society of mining-engineers, 
he referred to a number of authorities to show the 
important bearing dust-explosions have upon safety 
in mines, like this, apparently entirely free from fire- 
damp. Mr. J. Foster Crowell announced that the 
new bridge of the Pennsylvania Schuylkill valley rail- 
road, over the Schuylkill River at Manayunk, had 
just been completed, and noted, as a remarkable illus- 
tration of the vast strides made in American bridge- 
construction during the past few years, that so large 
and important structure as this is, being one-third of 
a mile in length and ninety feet high, can be reared 
and come into use without exciting special interest, or 
even deserving particular mention from an engineer- 
ing point of view. —— The secretary read, from Mr. 
J. H. Murphy, a discussion of the switch formulae by 
Mr. John Marston. —— Mr. A. R. Roberts described 
a contrivance he had designed, by which a three- 
throw point switch can be operated from a single 
stand. 
Linnaean society, New York. 
April 18. — Mr. E. P. Bicknell read the third in- 
stalment of his paper, ‘ A study of the singing of our 
birds,’ treating the Passeres to Astragalinus tristis 
in the same vein as the already published portions of 
this elaborate treatise. —— Mr. R. F. Pearsall called 
the attention of the society to the similarity of some 
of the notes of Parus atricapillus to those of Contopus 
virens, which accounted for the erroneous winter rec- 
ords of unseen individuals of the latter species. —— 
Mr. E. P. Bicknell related his spring observations for 
1884 at Riverdale, N.Y., upon the first appearance 
of birds, flowers, etc. —— A communication from 
Judge Bicknell of New Albany, Ind., stated thatthe 
English sparrow flew from that city to the ripening 
grain-fields, and hence the reduction, by one-half, of 
the promised crop. Only a very slight indulgence in. b 
a 
Tow ere SD 
