What ether remained in the above liquid was distilled off at 35° to 40° in a current of C,H. Even at this temperature a slight decomposition occurred (iodine separating), so I stopped heating. It was found practicable, however, to fractionate the liquid (with very slight decomposition) in a current of steam. Repeated fractionating yielded (1.) Ether+ CH2Cl2, &c. (not examined). (2.) C2H2CII+. (3.) Solid C2H2I2. To ascertain the composition of the above liquid I analysed it. +0.6687 grm. ignited with pure CaO gave (after converting AgI into AgCl by current of C1). The above figures do not agree very exactly, but I had too small a quantity of the compound to be able to fractionate it perfectly. It was found impossible to determine its boiling point, as it decomposed very rapidly on heating, with separation of iodine.* Spec. Grav. 2.41 at 13.5° C. Acetylene chlor-iodide is an ethereal liquid with much the same odour as the corresponding ethylene compound. Its vapour attacks the eyes. It does not decompose to any extent if kept in the dark. Remarks on Acetylene Iodide (C2H2I2). I prepared from 50 to 60 grms. of the above compound by passing the gas through a saturated alcoholic solution of iodine. As the two * It seemed to boil at first, on heating very rapidly, between 180° and 190° C., but this is not reliable. combine very slowly, the iodine must be distributed in numerous small flasks, which ought to be hung on a glass rod, horizontally placed, to admit of their being shaken from time to time. (See Sabanjeff, Annalen, Band 178; also Semenoff (for C2HI2), Zeitschrift für Chemie, 1864.) Sabanjeff states that he, while preparing the iodide in this manner, got at the same time a large quantity of a liquid iodide (also of the formula C,H,I,). He supposes the one to CH, CHI be || CHI Curiously enough, I only obtained a few drops of a liquid which could at all correspond to this second iodide. Whether it was the iodide, or a product of the action of the iodine in the alcohol, &c., I cannot say. The quantity got was too small. The chief object which I had in view in preparing the preceding acetylene compounds (chlor-iodide, iodide, also tetrabromide, &c.), was that from them I might be able to obtain the corresponding cyanogen ones, which, if got and treated with an alkali, would probably have yielded chloro- (or iodo-) acrylic, and fumaric or maleic acids. I have not, however, as yet succeeded in obtaining them. Whether C2H, combines with iodide of cyanogen when the latter is dissolved in alcohol, I cannot yet say. It does not with dry ICN. All attempts to obtain the cyanogen compounds of C2H, by heating in sealed tubes (at temperatures ranging from 120° to 0°25) chlor-iodide or iodide of acetylene with the various cyanides {KCN, AgCN, (AgCN+KCN), H2(CN2),} or with ICN and a metal, were fruitless. When H2(CN), was used, generally no reaction occurred, and in nearly all the other cases ammonium salts were formed in large quantity. I had unfortunately only a small quantity of the chloriodide at my disposal. Acetylene does not seem to be absorbed if passed into a hot solution of "nascent" formic acid, i.e., a solution containing KCN and KOH. a 82 0 4. On some Definite Integrals. By Professor Tait. The integrals referred to occur in connection with applications of the Method of Electric Images. A curious special case was given to the Society in July 1875, but was not inserted in the "Proceedings." It depended on the fact that the image of a sphere, whose surface density is inversely as the cube of the distance from a point, is another sphere with a similar law of distribution. But any desired number of integrals, whose values can be at once assigned, may be obtained by various applications of the following process. Take any centrobaric distribution of electricity, and calculate directly the density induced by it at any point of an uninsulated sphere. This must be inversely as the cube of the distance from the centre of gravity of the given distribution. Take, as a simple example, a uniformly charged sphere of nonconducting matter with unit charge, radius a, at a distance p from the centre of an uninsulated sphere of radius r. Suppose r >a+p, so that the inducing sphere is wholly internal. We see by the method above that the density of the induced charge at points defined by radii making an angle a with the line of centres is represented by 1 either of the following expressions, multiplied by 8T2r (r2 — a2 — p2+2ap cos 0) sin 0d0dp [r2+a2+p2 - 2ap cos 0-2rp cos a+2ar (cos a cos - sin a sin cos 4)]† ̄ ̄(r2+ p2 − 2rp cos a}} i.e., the double integral is independent of a. Again, if the unit charge on the small sphere be distributed inversely as the cube of the distance from the centre of the large one, we have obviously for the induced density on the large sphere the expression (a2 - p2) (r2 — a2-p2+2ap cos 0) sin Oded But if the small sphere include the centre of the large one, i.e., if 2π If a<p, similar reasoning shows that the value is These values agree, as they should do, when a=p. Monday, 1st April 1878. Sir WILLIAM THOMSON, President, in the Chair. The following communications were read : Chapter IV. By 1. Chapters on the Mineralogy of Scotland. (Abstract.) A couple of months ago I had the honour of submitting to the Society a speculation upon the metamorphism of a particular rock mass. To-night I again return to metamorphism, submitting, however, not a speculation, but the closely elaborated process of the change which has affected another rock. It is perhaps natural that the attention of one who approaches geology from the chemical and mineralogical sides should be immediately directed to those rocks which are either aggregates of simple minerals, or which are the products of changes effected upon simple minerals; natural also that consideration should be first given to those in which that change has been more immediately chemical than physical. To no rock mass does this apply more directly than to serpentine. In my wanderings I have visited and closely observed the relationship of-with a single exception-every bit of this rock which is to be found between Unst and Tyree on the one hand,-Harris and the Black Dog Rock on the other. In my analyses of a number of ill-defined minerals, generally believed to be products of the alteration of augite and hornblende, the subject recurred to me. In order to bring as much light to bear upon it as possible, I greatly extended the number of analyses which I undertook; and, as bearing upon it, I have now analysed 20 specimens of augite and its allomorphs, 15 of hornblende, and 21 of the products of the alteration of these two substances. Founding upon the information gained thereby, I work out chemically the various steps and stages of the transmutation,-which transmutation will be shown and seen to be the formation of serpentine. 2. On the Old Red Sandstone of Western Europe. By Professor Geikie, F.R.S. In a historical introduction the author gives an outline of the progress of research into the history of the Old Red Sandstone of the British area. This system is at present regarded as composed of three sub-divisions, Lower, Middle, and Upper, each characterised by a distinct suite of organic remains. From the absence of unequivocally marine fossils, and from lithological characters, it has been inferred by Mr Godwin Austin, Professor Ramsay, Professor Rupert Jones, as well as other observers, and is now very generally admitted, that the Old Red Sandstone, as distinguished from the "Devonian" rocks, probably originated in inland sheets of water. The object of the present memoir was to endeavour to trace out in that geological system of deposits the changes of physical geography which took place over Western Europe during the interval between the close of the Upper Silurian and the beginning of the Carboniferous period. After a sketch of the probable conditions of the region previous to the commencement of the Old Red Sandstone, the author proceeds to show how the shallowing Silurian sea was converted here and there into salinas or inland seas, by a series of subterranean movements, which have left their indelible traces upon the upturned Silurian rocks. He divides his memoir into two parts, the first dealing with the Lower and the second with the Upper Old Red Sandstone. The present paper deals only with a portion of the first of these sections. It traces out the limits of the different basins in which the Old Red Sandstone of the British islands were deposited, |