Mr. G. Gore on the Properties of Liquid Carbonic Acid. 485 



tables ; the latter exhibiting the amount of the lunar influence at 

 each of the 24 lunar hours, in the several magnetic elements at each 

 station. These data are directly applicable to inquiries into the 

 nature of the moon's magnetism ; and into the mode by wbich the 

 moon's magnetism acts either on the magnetism of the earth itself, 

 or on the magnetic needle stationed at different points of the earth's 

 surface, so as to produce a small but systematic and perfectly ap- 

 preciable variation in each of the magnetic elements, having a double 

 period in every lunar day. 



The lunar-diurnal variation of the Declination at Kew and Ho- 

 barton, as given in this communication, is slightly different from the 

 figures in the 2nd St. Helena volume referred to, because the results at 

 Kew are a mean of 3 years instead of 2, as in the St. Helena volume ; 

 and at Hobarton a lower standard has been taken for the disturb- 

 ances, causing a larger number of the disturbed observations to be 

 omitted in the calculation of the lunar-diurnal variation. 



January 24. — Major-General Sabine, Treas. and V.P., in the Chair. 



The following communications were read : — 



" On the Calculus of Symbols, with Applications to the Theory of 

 Differential Equations." By W. H. A. Russell, A.B. 



" On the Properties of Liquid Carbonic Acid." By G. Gore, Esq. 



In this communication the author has shown how a small quantity 

 of liquid carbonic acid may be readily and safely prepared in glass 

 tubes closed by stoppers of gutta percha, and be brought in a pure 

 state into contact with any solid substance upon which it may be de- 

 sired to ascertain its chemical or solvent action, or be submitted to the 

 action of electricity by means of wires introduced through the stoppers. 

 % By immersing about fifty substances in the liquid acid for various 

 periods of time, he has found that it is comparatively a chemically 

 inert substance, and not deoxidized by any ordinary deoxidizing 

 agent except the alkali-metals. Its solvent power is extremely 

 limited; it dissolves camphor freely, iodine sparingly, and a few 

 other bodies in small quantities ; it does not dissolve oxygen-salts, 

 and it does not redden solid extract of litmus ; it penetrates gutta 

 percha, dissolves out the dark-brown colouring matter, and leaves 

 the gutta percha undissolved, and much more white. It also acts in 

 a singular and somewhat similar manner upon india-rubber; the 

 india-rubber whilst in the liquid acid exhibits no change, but imme- 

 diately on being taken out it swells to at least six or eight times its 

 original dimensions, and then slowly contracts to its original volume, 

 evidently from expansion and liberation of absorbed carbonic acid ; 

 and it is found to be perfectly white throughout its substance. These 

 effects upon gutta percha and india-rubber may prove useful for 

 practical purposes. 



The liquid acid is a strong insulator of electricity ; sparks (from 

 a RuhmkorfFs coil) which would pass readily through ^nds of 

 an inch of cold air, would with difficulty pass through about 

 y 1 th of an inch of the liquid acid. 



In its general properties it is somewhat analogous to bisulphide of 

 carbon, but it possesses much less solvent power over fatty substances. 



