4368 
adds, ‘‘ We have hence the most certain, 
sensible decision and demonstration of two 
grand questions, which have, to this day, 
been doubtful and disputed among the. 
greatest masters of reason in the world. 
One is, that the planets, in their own na- 
ture, are opaque, attributing to Mercury 
what we have seen in Venus: and the other 
is, that Venus necessarily moves round the 
Sun; as also Mercury and the other pla- 
nets; a thing well believed indeed by Py- 
thagoras, Copernicus, Kepler and myself, 
but never yet proved, as now it is by oc- 
cular inspection on Venus.’’ Cassini and 
Campani, in the years 1665 and 1666, both 
discovered: spots in the face of Venus: the 
former ascertained her motion about her 
axis; concluding that this revolution was 
performed in less than a day; or, at least, 
that the bright spot which he observed, 
finished its period, either by revolution or 
libration, in about twenty-three hours. 
And Lahire, in 1690, through a telescope 
of sixteen feet, also observed spots. In 
1726, 1727, 1728, Signor Bianchini, at 
Rome, with Campani’s glasses, discovered 
several dark spots, of which he gave an 
account and a representation, in his book 
entitled Hesperi et Phosphori Nova Pheno- 
mena. Cassini the son, though he admits 
the accuracy of Bianchini’s observations, 
disputes the conclusion drawn from them, 
and finally observes, that if we suppose the 
period of the rotation of Venus to be 
twenty-three hours twenty minutes, it 
agrees equally well with the observations 
both of his father and Bianchini; but that, 
otherwise, his father’s observations must be 
rejected as of no consequence.. In Phil. 
Trans. 1792, are published the results of a 
course of observations on the planet Venus, 
begun in 1780, by M. Schroeter, of Lilien- 
thal, Bremen: from which it is inferred 
that Venus has an atmosphere similar to 
that of our earth, but far more dense than 
that of the moon; that her diurnal period 
is probably much longer than that of other 
planets ; and that her mountains are five 
or six times as high as those of the earth. 
Dr. Herschel too, between the years 1777 
and 1793, made a long series of observa- 
tions on this planet. The results are— 
that the planet revolves about her axis, but 
the time is uncertain: that the position of 
the axis is also uncertain: that the planet’s 
atmosphere is very considerable : that there 
are probably hills and inequalities, of which 
he has not been able to see much, owing 
perhaps to the density of the atmosphere : 
and that the apparent diameter of Venus, 
at mean distance from the earth, is 18” 79” ; 
whence it appears, that-this planet is some- 
what larger, instead of being less than the 
earth. Sometimes Venus is seen in the disk 
of the sun,.in form of a round dark spot. 
This,appearance, called a transit, happens 
butseldom ; viz. when the earth is about 
her,nodes atthe time of her inferior con- 
unction... One. of these transits was seen, 
Spirit of Philosophical Discovery. 
[Dec. I, 
in England, in 1639, by Mr. Horrox and 
Mr. Crabtree ; and two in the last century, 
viz. one on June 6, 1761, the other in June 
1769. Another will not happen till 1874. 
In 1672 and 1686, Cassini, with a teles- 
cope of thirty-four feet, thought, As 
satellite move round this planet, at the 
tance of about three-fifths of her ieieter.. 
It had the same phases as Venus, but with- 
out any well-defined form ; and its diameter 
scarcely exceeded one- -fourth of her diameter. 
Dr. Gregory and others support this obser- 
vation; and suppose that the reason why 
it is not more frequently seen, is the unfit- 
ness of the planet’ s surface to reflect the 
rays of the sun’s light, as is the case in the 
spots of the moon. 
Pectic Acid, lately so named by M. H. 
Braconnot, exists, mostly in the form of a 
jelly, in the roots and other parts of most 
vegetables: the pectate of potash .(com- 
posed of eighty-five acid, and fifteen potash), 
as prepared from the roots of turnips, dis- 
solyed in warm water, in which sugar was 
then copiously dissolved, and on the addition 
of a very small quantity of the acid, in an 
instant afterwards, the whole became a 
trembling gelatinous mass, weighing 300 
times the weight of salt dissolved... In this 
way, says M. B., the confectioner, may 
cheaply prepare aromatic jellies, perfeetly 
transparent and colourless, and very agree- 
able to the taste and sight.—Ann. de Chim. 
vol. 28. 
Bi-carburet of Hydrogen, a new sub- 
stance, has been discovered and separated 
by Mr. Faraday, from a colourless fluid, 
lighter than water, which, in’ considerable 
quantities, forms in the bottoms. of the 
vessels in which the Portable Oil-Gas 
Company compress the gas for filling their 
lamps. The new substance, in its liquid 
form, between 42° and 86° Fahr., is com- 
posed of two atoms of carbon and one of 
hydrogen. When in the state of vapour, 
six atoms of carbon and three of hydrogen 
are present to form one volume, of thirty- 
nine times the specific gravity of hydrogen. 
Below 42° of temperature, it is a solid 
body, forming dendritical transparent ¢rys- 
tals: at 0°, it has the whiteness and hard- 
ness, nearly, of loaf-sugar. 
Emetic Tartar, as usually sold ‘by the 
druggists, in powder, is found to be adul- 
terated to the extent of ten per cent. at the 
least, by tartrate of lime, and super-tartrate 
of potash: and medical practitioners, are 
earnestly recommended to use only. the 
crystals of emetic tartar, in preparing anti- 
monial wine, or other medicines, 24 FB 
Perpetual’ Motion.—M. Jean’ Préve, ‘of 
Marseilles, has announced'a machine of his 
invention, which preserves and ‘conmmuni- 
cates a perpetual motion.'* ‘This isyateast, 
the hundredth discovery “of a’'similar’ na- 
ture that has been proclaimed owithin’ our 
recollection.» iat si Dain bis 
‘ 1 to bao 
