1825.] 
blocks of glass, containing portions perfectly 
homogeneous ; these he separated, by saw- 
ing the blocks into sections, selecting those 
parts which were free from defects, and re- 
turning the others to the crucible. After- 
wards he improyed upon this process, by 
casting his glassin moulds. The refraction 
of M. Guinand’s glass varied at almost 
every casting ; but the whole mass was 
always so perfectly homogeneous, that any 
tivo portions, taken from the topand bottom 
of the erucible, had the same refractive 
power. M. Guinand obtained such repu- 
tation by the manufacture of achromatic 
telescopes from this. glass, that he was 
visited by many scientific men from differ- 
ent parts of Europe; and, in 1805, was 
called into Bavaria, 250 miles from_ his 
home, in the employment of M. Frauen- 
hofer, a celebrated optician. Here he con- 
- tinued nine years, occupied almost solely in 
the manufacture of glass; and it is from 
this period thatM. Frauenhofer’s achromatic 
telescopes have acquired so well-merited a 
reputation. After returning from Bavaria 
to his native country, M. Guinand carried 
his distovery to a still higher degree. of per- 
fection; and, in the last years of his life, 
succeeded in manufacturing discs of eleyen 
or twelve inches (English measure) per- 
fectly homogeneous, and free from defects. 
The pecuniary circumstances of M. G. 
preyented his divulging the process of 
manufacturing glass; but arrangements 
had been made by the French government 
to purchase the secret, when the artist, 
verging on his eightieth year, died after a 
short illness. His son remains in posses- 
sion of the process, and it is hoped that an 
improvement, which opens the way to such 
important acquisitions in the field of astro- 
nomical research, will not be lost.—Am. 
Journal. : 
_ Inhabitants of the Moon.—Several learn- 
ed. persons have gone near to the actual 
yerification of an often laughed-at, but now 
apparently prophetic sentence (penned ra-. 
ther in doubt than in expectation) in Bon- 
nycastle’s Astronomy (p. 312). ‘‘ We can 
hardly hope to make optical instruments 
sufficiently perfect, to render animals visible 
at such a distance;” nay, it is eyen said, 
that, using Sfrayel’s new telescope, (M. M. 
No. 414, p. 166,) animated beings, roads, 
monuments, temples, &c. have been dis- 
covered on the surface of the moon. 
The vital functions of the sponge have 
been recently made the subject of some 
very attentive researches, by Dr. Grant, of 
Edinburgh, which were communicated to 
the Wernerian Society at a late sitting. 
Dr. Grant placed two portions of. sponge 
(spongia panicea) taken from the rocks in 
the Frith of Forth, ina glass of sea-water, 
with their orifices opposite to each other, 
at the distatice of two inches, when they 
soon covered each other with feculent mat- 
fer- He then placed one of them in a 
Spirit of Philosophical Discovery. 
243 
shallow vessel, and just covered its sur- 
face with water: on strewing some pow- 
dered chalk on the surface of the water, 
currents were perceptible, at a great dis- 
tance, and bits of cork or paper were driven 
to the distance of ten feet. <A piece of 
coal was repeatedly placed on the orifice 
(which may be called the rectum of the 
sponge), and as invariably displaced-by the 
eurrent of water ejected. A globule of 
mercury dropped on the aperture, how- 
ever, stopped the process until another ori- 
fice was made, in the vicinity, by means of 
a needle, when the current was renewed, 
and continued even when the original ori- 
fice was again opened. By adopting this 
plan, Dr. G. clearly ascertained that the 
current of water never enters by the same 
apertures through which it issues, and 
although he employed the microscope in 
his experiments, yet the process is dis- 
tinctly perceptible to the naked eye. It 
thus appears that the round apertures on 
the surface of a sponge, are destined for 
the conveyance of a constant stream of 
water from the interior of the body ; the 
stream carrying off the excrementitious mat- 
ter, which may be perceived in whitish 
flakes, depositing themselves on the bot- 
tom of a confined vessel. By the aid of 
the microscope, certain small round bodies, 
of-an opake yellow colour, were also ob- 
served to be ejected, which Dr. G. con- 
siders as the ova of this interesting class of 
marine animals, formerly considered as be- 
longing to the vegetable kingdom. 
Spots on the Sun’s Dise have appeared 
very numerous, and occupying a large 
space, the extent from the uppermost to 
the lowest being equal to 111,386 miles. 
Sir William Herschel attributes these spots 
to the emission of an aériform fluid, not yet 
in combustion, displacing the great luminous 
atmosphere, which is afterwards itself to 
serve the purpose of supporting combustion. 
Hence he supposed the appearance of se- 
veral spots to be indicative of the approach 
of warm seasons, and he has attempted to 
maintain his opinion by historical evidence. 
How remarkably the hot weather and the 
appearance of solar spots, this summer, illus- 
trate and confirm this theory —Mr. Emmett 
has made many observations on these won- 
der-raising appearances, all of which tend 
to disprove such regularity of motion, as to 
bring them into or hide them from sight, 
for equal portions of time ; while they con- 
firm the opinion of older philosophers, as 
to the opposite belief. According to Mr. 
E., they 'remain visible twelve days eight 
and a half hours, and invisible fifteen days 
three and a half hours ; which nearly agrees 
with the times given by Kirchius, Stan- 
nyan, Cassini, &e.; and no imperfection 
of instruments, nor inaccuracy of observa- 
tion, can fairly be urged to account for the 
difference between these and equal times. 
212 PROCEEDINGS 
