Scientific Intelligence —Mechanical Philosophy. ~ 389 
earth having been previously allowed to dry freely. In this manner 
it-was found that the neutral solutions of acetate of mercury, acetate 
of lead, sulphate of copper, muriate of tin, muriate-of manganese, ni- 
trate of cobalt, nitrate of bismuth, tartrate of antimony, muriate of 
baryta, muriate of strontia, and solutions of white arsenic and dilute 
prussic acid, destroyed plants previously full of vigor, either in the 
course of a few days, or a week. On the contrary, solutions of the 
sulphate of iron and zinc, muriates of titanium, iron and lime, and sul- 
phates of alumina and magnesia, produce no prejudicial action. 
When sought for, all the substances used were found in the plants, 
so that in opposition to what Mr. Murray has said, absorption. had 
taken place by the roots. rer By 
Solutions. of opium, hemlock, henbane, digitalis, and vomica 
nut, in the proportion of twenty grains of extract in two ounces:of 
distilled water, poured into pots containing young plants of the family 
Chénopodus, caused death in from four to eight days. 
Phillips’ experiment of watering a plant with sulphate of copper, 
and killing it, was repeated, also, the absorption of copper and its pre- 
cipitation on a knife verified. Solution of four ounces of acetate of 
lead applied to a young willow did not kill it, probably because the 
carbonic acid disengaged by the roots precipitated the metal. . Asim- 
ilar experiment with two ounces of white arsenic, only made the tree 
to which it was applied grow more rapidly, M. Weigmann thinks 
that because the arsenic was-in too small a quantity, and. acted only- 
as a stimulant.—Idem. | Ae 
MECHANICAL PHILOSOPHY. 
1. Resistance in Space to the Motion of Heavenly Bodies. (Bib. 
Univ. XLI. 3.)—In an account of the last appearance of Encke’s 
Comet in 1828, M. Gautier states, that the results then obtained, ac- 
corded with those which Encke had previously procured, and which 
induced him, in 1823, to suppose the existence of a medium or ethe- 
rial fluid in space, of which the resistance, acting as a tangential force 
against the motion of the comet, would augment the power of the sun, 
and shorten the period of revolution. ‘The most celebrated geome- 
ters, and even Newton himself, had already calculated the influence 
which such a resisting medium could exercise on the motions of com- 
ets and planets. ‘They had found that its effects would be to dimin- 
ish continually the eccentricity of their orbits, and to shorten the lon- 
ger axes and the periods of their revolutions ; that the length of the: 
