Miscellanies. 377 



rounding air. The second appears most plausible, since it is diffi- 

 cult to admit the first, when we attend to the conducting power 

 of the flame, and of the column of hot air, which is much superior 

 to that of the leaves. The results of a great number of observations, 

 proved that in the night, Signs of electricity are often absent, both 

 in the air and the interior of a wood. At the approach of day, be- 

 fore the sun appears above the horizon, decided indications of nega- 

 tive electricity appear among the trees, while none are detected in 

 the open air. We can readily understand this observation, if we 

 admit that oxygen is disengaged from the leaves, before the rays of 



the sun strike them directly. In this case, negative electricity ap- 

 pears. From the above it may be inferred, that negative electricity 

 is disengaged by vegetation during the day, which is constantly neu- 

 tralized by positive electricity. • 



Effect of 



(Records of General Sci- 



ence, No. xiv. 1836, p. 113.) — Sir H. Englefield, while at Brus- 

 sels in 1773, made some experiments on this subject. The barom- 

 eter was fixed in the opening of a window, in the north east tower 

 of the church of St. Gudule, about seven feet from the summit of the 

 bell. Mr. Pigott found the height of the barometer, 29.478 inches. 

 It did not vary until the clapper was loosened, when the mercury 

 rose and continued to undergo a kind of starting, every time the 

 clapper struck the bell. Mr. Pigott observed the height of the mer- 

 cury during the sound 29.469. Sir H. Englefield, found its max- 

 imum height, during the sounding 29.480, minimum 29.474 ; max- 

 imum 29.482, minimum 29.472. Hence the effect of sound upon 

 the barometer, extends to the * 7 V* and TI i^ of an inch. It is 



» 



remarkable that Pigott generally made the height jyVi ' ess t ' ian 

 Eno-lefield. The latter attributes such discordances to the differ- 

 ence in the eyesight. 



CHEMISTRY. 



1. Phloridzine; anew organic substance. (L' Institut. No. 143.) 

 This vegetable principle was obtained by MM. de Koninck and 

 Stas from the bark of the root of the apple, pear and cherry trees. 

 It may be procured by boiling the roots for four or five hours in wa- 

 ter, decanting the liquid and continuing the ebullition with an addi- 

 tion of pure water for two hours, and again decanting. The decant- 

 ed liquid, in each instance, after twenty four or thirty six hours repose, 



Vol. XXX.— No'. 2. " 48 



