340 
loric. And this divergence appears to pro- 
ceed in an increasing ratio, as we recede 
from the point of zero. Independent, how- 
ever, of this, objection to spirit thermome- 
ters, where very, accurate obseryations are 
required, the sources/of error will of course 
be magnified, if thermometers be filled with 
spirit of wine, of. different spec. gray. ; 
which is probably, often the case in the or- 
oe manufacture of these instruments. 
Yew Optical Instrument, or Water-Teles- 
poy obs the last number of the Journal of 
Science, the following account.of an in- 
genious inyention is given :—An optical in- 
strument for seeing through water, and ex- 
ploring the bottom of rivers, has been con- 
structed, by, Mr. Keslie,..of Lansonburgh, 
United States. It consists of a, conical tube 
of variable length, about an inch broad at 
the top, and ten inches at the botton. It 
is glazed at, both ends, and when the broad 
end is immersed to. some depth in water, 
and the eye applied at the narrow extremity, 
there is no interruption to, or deflection of 
the rays of light coming from objects in the 
water to the eye ; and if the water be clear, 
objects may be distinctly seen to a consider- 
able depth. The instrument is provided 
with lamps suspended near the lower or 
broad end, in’an outer cylinder, which slides 
on over what may be termed the object 
glass of the instrument. The light of the 
lamps being reflected towards the bottom, 
any. object may be easily distinguished by 
night, if the water be clear. Two tubes 
are attached to the cylinder, containing the 
lamps ; one to supply fresh air for the com- 
bustion, and the other to carry off the smoke 
and foul air. The account does riot 
state whether the glasses of- this water- 
telescope are plain or magnifiers. We see 
no reason why convex glasses may not be 
employed in this as in other telescopes. 
Method: of distinguishing positive from ne- 
gative Electricity.—The celebrated chemist 
Berzelius finds, that when the electric cur- 
rent passes by means of a point to the 
tongue, the positive electricity is acid ; and 
the negative electricity a mere caustic acid, 
or rather alkaline. 
Inflammation of sulphuretted Hydrogen by 
Nitric Acid.—M. Berzelius has found that- 
if afew drops of the nitrous acid be poured 
into a flask, containing four or five cubic 
inches ofsulphuretted hydrogen, and the flask 
closed with the finger, it becomes so warm 
as to produce combustion, ‘with a beautiful 
flame, and a slight detonation, which forces 
the finger from the mouth of the flask. It 
is necessary that the) acid should be very 
pure for this purpose, and that the gas 
should be free from aqueous vapour. 
BenzxsieAcid in Oil of Dahlia. —The French 
chemist, M. Payen; in Seaeteay on 
Spirit of Philosophical Discovery. 
[Nov. 1 
the essential oil obtained from that beautiful 
plant the Dahlia, found a erystallizable sub- 
stance perfectly analogous to the Benzoic 
acid. Do not several varieties off the aro- 
matic plants yield a, similar substance ?, The 
Benzoic acid being in flavour not unlike the 
essential oil of lemons... The. citric, acid 
when pure, and a yery small portion of the 
flowers of Benjamin added, is a good sub- 
stitute for recent lemons, when that whole- 
some and agreeable fruit cannot_be ob- 
tained. 
_ The Chickin Ovo, Sc: —Mr: David Ritchie, 
im_a notice of a mode by which a conjecture 
may be formed as to the sex of ‘a ehick in 
ovo, after combating former ‘theories as to 
shape, weight, &c. &e. says—‘* Thave heard 
of a mode of discovering the sex of the chick 
in ovo, different from any which has been 
proposed by naturalists. The folliculus 
aéris, or air-cell, which is to farnish oxygen. 
to the future chick, is situated at the larger 
end of the egg. It has not in all eggs the 
same position at the larger end; and in va- 
rious districts of Scotland, it is believed that, 
eggs having the air-cell situated ewactly at 
the top of the larger end, produce males; 
while those having the air-cell only ear the 
top of the larger end produce females. To 
ascertain this, I instituted a series of expe- 
riments. ‘These experiments, as will be 
seen, go very far'to prove that the opinion 
which has been stated is correct, and so to 
determine what naturalists of Germany, 
France, and England, have endeavoured in 
vain to discover.—Ed. Phil. Journ. 
Preserving of Birds, &¢.—Sir John Sin- 
clair has communicated to us the following 
notice: Mr. Temminck, Director of the 
Dutch Museum, has, for many years, made 
use of no other means of saving preserved 
birds and quadrupeds from the attacks of 
minute insects, than placing a Small wooden 
basin, containing tallow, in each case, which 
he finds to be more’ effectual ‘than either 
camphor or Russia leather.—Ib, 
Medical Remains at Pompeii.—M. Chou- 
lant has lately published, ‘at Leipsic, in a 
pamphlet, entitled De Locis Pompeianis ad 
Rem Medicam’ facientibus, an account of 
different objects relating to the medical 
art. discovered at Pompeii. M. C.’ ‘suc- 
cessively describes’ the Temple of Estu-. 
lapius, the amulets, surgical instruments, 
pharmaceutical apparatus, &c. found in the 
midst of the ruins. Amongst the surgical 
instruments were found some nearly resem- 
bling those made use of at the present day ; 
as, for instance, elevators for the operation 
of trepanning, lancets, spatulz, instruments 
for the application of the actual cautery, &c. 
There has not been found one single build-— 
ing which could be regarded as a school of f 
surgery or anatomical museum. —Tb. 
PopHG, 
voOv 
Poss te 
