154 Scientific Correspondence.’ 
and silica together, and gives the sum as olivine; these substances are 
obviously not in the proportions to form the silicate 3RO, SiOg, and if 
we consider the silicate to be olivine, we must reckon the excess of silica 
as combined with protoxyd of iron. To do this, we must deduct 2°83 
from the amount of metailic iron (equal to 3°64 protoxyd of iron), neces- 
sary to be combined with the silica and magnesia to give the olivine 
n 
will then be 8-70 per cent. Thus the two masses of iron will be seen to 
agree very nearly in composition, the only trifling difference being, that 
Dr. Smith has determined quantitatively the small amount of chromium 
contained in the Bartlett meteorite, whilé I have found a little lime and 
fore of es. and oe in the specimen you sent to me. 
specific gravity I have stated to be.7:29; this was taken on about 125 
grammes of the iron, et sibalis | is somewhat higher than the portion 
which I analyzed, as the two surfaces of the larger specimen had 
rubbed down, and as thus a considerable portion of the exposed silicate 
would be mechanically removed, it would make the density corto ue 
ingly higher. E 
. Meteor of April 19th seen at Philadelphia. —A brilliant mould as 
was seen at pal gst and vicinity, on Sunday evening, April 19th, 
o'clock, 
at 10 minutes ‘halore ; 
ts apparent size was oagor less than that of the full moon, its brillianey 
considerably greater, form globular, and direction of motion nearly from 
west to east, tending slightly southward. 
It seems pr obable that its first appearance was over the eastern edge of 
Chester County, although the data are not sufficient to determine satis- 
factorily either the place of beginning or the velocity. It is very clearly 
. P 
Town (4 miles east of West Chester), Wilmington and Odessa, 
that it get ter over the — ee of Camden County, i 
The Seaton of visibility was estimated at from 3 to 6 seconds. 
Both at Wilmington a and West To own, it was — pa an interval 
of about 3 minutes, by a noise like thunder. the former place, @ 
gentleman who did not see the meteor woibg Joc oe poe to that of 
cannon at Fort Delaware. ten miles dist 
VI. SCIENTIFIC CORRESPONDENCE. — Observations on Stellar Spec 
eseribed i in their Oise a Donat used a large burni 
tha ike nches aperture rab c sronca inches focal distance, 
atorially, the ¢ light hroug 
sary 9,166. oy, Apri 10, 1368. ‘ vo hy 
