During the cruise of H.M.S. “ Triton ” a small but very interesting collection of Pycnogonids was made. Mr John Mueray sent it over to me, and asked me to prepare a report on it, which I gladly undertook to do.

On a moonless night, whenever clouds of an ordinary elevation in the atmosphere appear upon, or pass across, the star-spangled sky behind them, they exhibit themselves, as a rule, dark, sometimes even black, in comparison therewith. And no wonder, when every part of the open sky from visible star to visible star therein must be lit up to some, though doubtless a very small, extent by the faintest general and cumulative radiance of those myriads and myriads of lesser stars, which only a large telescope can show to be individually existent as actual stellar points of light, but in their aggregate more nearly eternal, and still more constant from age to age, than our gigantic Sun itself.

Every spectroscopist is perfectly aware that the group of dark Fraunhofer lines in the Solar Spectrum, known as “ little b,” is composed of the biggest, broadest, most colossal lines in all the brighter part of any and every spectrum depending on Sunlight, whether direct from the Sun or reflected from the earth's atmosphere, the Moon, or any of the planets.

Having undertaken to continue the observations on the growth of trees commenced by my father in 1878, and carried on by him with unflagging zeal until a few months before his death in 1882, I give in the present paper the measurements made by him in 1881, which he did not live to publish, and those made in 1882 by myself. I shall also endeavour to point out the conclusions which may be drawn from the whole series of observations, beginning in 1878, arranging them under the heads of—

I. Annual Observations.

II. Monthly Observations.

III. Influence of Weather on the Growth of Wood.

Introductory.—In the course of an inquiry into the physiological and therapeutical action of alkaline nitrites, and allied substances, I was struck with the strong resemblance which the action of nitroglycerine bears to that of the nitrites. The resemblance is, indeed, so well marked, that the action of the one may be held to be identical with that of the other, unless in respect of intensity. The suggestion, therefore, naturally occurred to me, that nitroglycerine is not a nitrate of glyceryl, as it is always represented, but a nitrite. For no ordinary nitrate, as an alkaline nitrate or nitrate of ethyl, nor any compound of glyceryl with another acid, as sulphuric acid, produces an action on the body at all resembling that of nitroglycerine. On referring to the various investigations which had been made for the purpose of ascertaining the chemical constitution of nitroglycerine, I found that none of them was sufficiently extended and exact to place beyond doubt its precise nature. The danger in manipulating so explosive a body had evidently prevented the various chemists from making a thorough examination of its composition. I at first thought that nitroglycerine might be a nitrite of glyceryl, having its nitrous acid so intimately combined with the glyceryl, that the acid did not exhibit its reactions when tested for in the usual way ; just as the acids of other ethereal compounds will not yield their usual reactions, unless special means are taken to forcibly dissociate the acid from the base ; for example, the acid of acetate of ethyl, or of chloride of ethyl. Certainly nitroglycerine gives no blue colour with a solution of starch and iodide of potassium and sulphuric acid, a very delicate test for the presence of nitrous acid. In order, however, to apply the test to the separated acid of nitroglycerine, I mixed an alcoholic solution of nitroglycerine with an alcoholic solution of pure caustic potash. The potash was ascertained to be free from nitrite, which I have frequently found present in small quantity in various specimens of ordinary potash. Decomposition of the nitroglycerine quickly occurred, and the fluid, when now tested for nitrous acid, was found to contain the acid in abundance, and so much of it, that for the moment I believed that nitroglycerine was, in reality, a nitrite of glyceryl; and hence the nature of its physiological action. Some estimations, however, of the quantity of the nitrous acid proved to me that whilst the larger portion of the nitrogen of the nitroglycerine appeared as nitrous acid in the decomposed products, yet a considerable portion was present in some other form.

Nitroglycerine is commonly described as the tri-nitric ether of glyceryl, and the formula C3H5(O.NO2)3 is accorded to it. This theory of its composition is based (1) upon its mode of formation; (2) upon the statement, made by Railton, Williamson, and others, that it is decomposed by potash into potassium nitrate and glycerine; (3) upon several estimations of the nitrogen which it contains, and one comparative estimation of its carbon. The second argument cannot be accepted, as it has been shown by one of us that the decomposition does not take place in the way stated; and the analytical results which have been obtained by the various investigators are so incomplete and mostly so imperfect, and differ so greatly among themselves, that they cannot be taken as affording any proof of the composition of the substance. It seemed to us, therefore, desirable that some accurate estimations should be obtained, not only of the nitrogen but of the carbon and hydrogen. A brief résume of previous analytical results will show that this is the case.

This collection was sent to me for examination some months ago by Mr Murray. It may be conveniently divided into two very natural groups:—

1. Ascidiacea, including the forms dredged or trawled from the bottom of the sea.

2. Thaliacea, including the free-swimming pelagic forms captured by the tow-net at or below the surface.

The Pennatulida obtained by H.M.S. “Triton,” and placed in my hands for description, are of six genera only, each genus being represented by a single species. The interest of the collection is, however, far from commensurate with its size, for of the six species two are altogether new to science, a third has hitherto been met with only off the Norwegian coast, while concerning the remainder, which are well known species, the “Triton” specimens have furnished important additions to our knowledge, either of their anatomy or distribution.

The star-fishes recorded in the present communication were dredged by Mr John Murray during the cruise of H.M.S. “Triton” (under the command of Staff-Commander Tizard, R.K), whilst investigating the nature of the Wyville-Thomson Ridge and the adjacent portions of the Faeröe Channel. All the forms, excepting these from Station 3, were obtained from deep water, and the collection, as a whole, is both rich and interesting. One species and two well-marked varieties have not hitherto been described, and two other species have only been found once previously. The series consequently forms a valuable supplement to the collections made during the cruises of H.M.S. “Porcupine” and the “Knight Errant,” and is an important addition to our knowledge of the fauna of this region of the Atlantic. I propose to reserve any remarks upon the general character of the asterid fauna of the Faeröe Channel until treating of the collections obtained during the “Porcupine” and “Lightning” cruises.

For the parasites which form the subject of the present communication, I am indebted to my friend Professor Morrison Watson, who found them in a male specimen of Proteles cristatus, Sparrman, of whose myology he has since published an account. Before entering upon a description of the entozoon, it may be allowable to say a word or two with respect to its host, which is not an animal of everyday occurrence. It was first described a little more than a century ago by Sparrman, the Swedish traveller, as occurring in South Africa, where it is known to the farmers as the “grey jackal”; he gave it the name Viverra cristata. The only point in his description of any present interest is that its stomach “ had nothing but ants in it, or to speak more properly, the white termites,” which might be a valuable hint for any one who had the will and opportunity to investigate the life history of the parasite before us.

The experiments which form the subject of this paper are designed, in the first place, to test the relation pointed out by Maxwell between Joule's discovery of the lengthening of iron in the direction of magnetisation, and Wiedemann's later researches into the twisting of iron under the influence of longitudinal and circular magnetisations, and, in the second place, to investigate the corresponding properties of nickel.

The experiments contained in this memoir were made by the author with the galvanometer on wrought iron, steel, cast metal, &c, bars and plates, arranged in galvanic circuit in sea-water and various other waters and solutions, to determine the relative electro-chemical position of these metals under such circumstances.