By the foregoing experiments, concludes Mr. Ritter, which though capable of the most various modifications, uniformly coincide in their main result, it is abundantly proved that _galvanic circles can be formed of merely inorganic bodies, by whose completion there is produced an action which ceases when the circle is opened_. The manner in which this has been shewn, proves also that _this action can effectuate sensible modifications in organic bodies_; and the process by which these modifications have been effected, made it evident that they _were not consequences of a momentary action of the circle, but of an action that is kept up while the circle remains entire_; for the process which brought this action under the cognizance of the senses went on, while the circle was unbroken, and its figure not brought back to that of a line. It is scarce necessary to observe that the experiments here quoted, are far from being the only ones on which the above conclusions rest.” _T. B._ _d._ In Res. II. Div. I. it is stated, that nitrous oxide during its solution by common water, expels about ¹/₁₆ of atmospheric air the volume of the water being unity. From the delicate experiments of Dr. Pearson, on the passage of the electric spark through water, it appears however probable, that much more than ¹/₁₆ of atmospheric air is sometimes held in solution by that fluid,[239] possibly the whole of the air is not expelled by nitrous oxide, owing to some unknown law of saturation by which an equilibrium of affinity is produced, forming a triple compound. [239] Possibly a ratio exists between the solubility of gases in water, and the solubility of water in gases. It is probable from Mr. Wm. Henry’s curious experiments on the muriatic acid, that the absolute quantity of water in _many_ gases, may be ascertained by means of its decomposition by the electric spark. No. IV. DESCRIPTION OF A MERCURIAL AIRHOLDER. Suggested by an inspection of Mr. WATT’S Machine for containing Factitious Airs. _By WILLIAM CLAYFIELD_. Several modes of counteracting the pressure of a decreasing column of mercury having been thought of in conjunction with Mr. W. Cox, the following was at last adopted as the most simple and effectual. Plate 1 Fig. 1, represents a section of the machine, which consists of a strong glass cylinder A cemented to one of the same kind B, fitted to the solid block C, into which the glass tube D is cemented for conveying air into the moveable receiver E. The brass axis F, Fig. 2, having a double bearing at _a_, _a_, is terminated at one end by the wheel G, the circumference of which is equal to the depth of the receiver, so that it may be drawn to the surface of the mercury by the cord _b_ in one revolution; to the other end is fitted the wheel H, over which the balance cord _c_ runs in an opposite direction in the spiral groove _e_, a front view of the wheel H is shewn at Fig. 3.