On the 16th of February 1880 I communicated to the Society a research upon Comets, which led me to believe in the existence of two new planets outside the orbit of Neptune. This memoir was not published in the “Transactions,” and only a short abstract appeared in the Proceedings of the Society. A small number of copies were privately printed; but any one wishing for information on the subject will find it most readily in the “Observatory,” 1880, June 1.

The decided tendency of the aphelia of comets to group themselves at distances from the sun equal to those of the planets could leave no doubt about the existence of these two new planets. The only doubtful point was as to the positions of the planets in their orbits. Meantime this research gives us greater confidence in the accuracy of the orbits of comets which have been calculated. This is most especially the case with the periods of revolution of comets when those periods are long, an element which has hitherto been very generally mistrusted. The most remarkable case is that of the comet 1861, which was calculated by Oppolzer to have a period of 415 years, and which I showed to have returned. three times at such an interval.

I am indebted to the kindness of my friend Mr J. Y. Buchanan, M.A., the chemist and physicist to the “Challenger” expedition for the specimen which forms the subject of this note.

In speaking of the geology of Kerguelen Island, Mr Buchanan thus describes the occurrence of this zeolite (vide Proc. Roy. Soc., vol. xxiv. p. 617).

“The horizontal beds which form the mass of the land are basaltic, and vary from 10 to 20 feet in thickness, being generally compact; but, in ascending the hill, beds are met with frequently, which contain large amygdaloidal cavities filled with zeolites, principally analcite and heulandite (stilbite). These minerals are very plentiful in this part of the island, and when rounded by the action of the water they form remarkable white pebbles on the otherwise darkcoloured volcanic sand. Up to the summit the alternation of beds of compact sub-columnar rock of amygdaloid is pretty regular.

The cell is constructed as follows:—

Take a brass crop-comb of the kind usually worn by little girls. Cut off from it two equal parts, each about 4 inches long. From each part cut out each alternate tooth, and bend round each part in the form of a cylinder, soldering the ends together with hard solder. Take a glass tube about 4 inches long and having a diameter equal to the diameter of the cylinder. Place the brass cylinders upon the glass tube, with the teeth facing each other, and adjust them so that each tooth left takes the place of one which has been cut out, taking care that the teeth do not touch each other nor the solid parts of the cylinder.

Since I made my first communication to this Society on Dust, Fogs, and Clouds, most of the experiments have been repeated under different conditions.

Taking advantage of the late extremely cold weather, the apparatus was placed in the open air, and experiments made with it, the temperature of the air at the time being 8° Fahr. The result was the same as at higher temperatures. Cloudy condensation with dusty air; no condensation with filtered air.

The experiment in which dustless gas was burned in dustless air was repeated. The glass jet which was used for burning the gas in the first experiment, being now replaced by a platinum one, as it was thought possible the dust produced when the glass jet was used might be the result of the decomposition of the glass by the heat. Before makiug the experiment, the platinum jet was highly heated, to cleanse and make it inactive. The result, however, was as before. Dense fogging whenever the gas was lit, and the fogging continued so long as the gas was kept burning.

In the great majority, at least, of investigations (experimental or mathematical) connected with conduction of heat, it has been assumed that the known changes of specific heat of metals do not require to be taken into account. Thus Ångström says, even in his paper on the Change of Conductivity with temperature (Pogg. 118, 1863):—“Da indess diese Veränderungen, soweit man sie kennt wenigstens innerhalb der bei den Beobachtungen vorkommenden Temperaturgränzen, nicht bedeutend sind, …,… so müssen dieselben den Werth des Wärmecoefficienten nur unbedeutend afficiren können.”

Since Henle and Purkinje first described the cells which form the great mass of the liver, microscopists have maintained that these are what are termed “naked protoplasts”—that is, they possess, like the white blood corpuscle, no differentiated cell-walls. I may mention the names of Dr Lionel Beale, Ewald Hering (“Stricker's Histology,” section on the Liver), and Dr Klein (“Atlas of Histology”), who all agree in denying its existence. Indeed, the absence of this structure is emphatically insisted upon in most works on microscopical anatomy.

If a liver-cell be examined with a power of about 300 diameters, it is seen to be a granular mass, of a somewhat spherical shape, containing a very distinct nucleus and nucleolus. The granules are but the optical expression of a delicate reticulum or stroma, which may be seen as such on using a higher power.