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. 



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 

 Chenopodus, 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. A sim- 

 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.— Jc/em. 



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 augrnent 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 



