freezing-point, excretine crystallizes readily and in large quantity in the clear alcoholic extract of fæces; this method I employed as often as possible, to prepare enough excretine for its chemical analysis; but the cold weather not lasting long enough, and this season having been remarkably mild, I was compelled to adopt a modification of the process by milk of lime, described in my former communication.

Having prepared a sufficient quantity of excretine, partly by the action of cold, and partly by means of milk of lime, the chemical composition of this substance was now determined. A qualitative analysis showed it to consist of carbon, hydrogen, sulphur and oxygen*; there was no water of crystallization present. Oxide of copper was employed at first for the combustions, but they were subsequently undertaken with chromate of lead, on account of the large proportion of carbon that excretine contains; no substance having been found to combine with it, its atomic composition was calculated from the assumption that one equivalent contained one equivalent of sulphur; and the following formula was obtained :

I shall not add more at present as to the properties of excretine ; the plate which accompanies the paper illustrates the shape and arrangement of its crystals.

In my former communication I had stated that when the tissue of the spleen is submitted to a process of analysis similar to that adopted for the extraction of excretine, a substance closely allied to cholesterine is obtained. This subject being one of great importance in a physiological point of view, I have resumed the investigation, and placed beyond doubt that this substance is really cholesterine. Its

In my former communication I had erroneously stated that excretine contained nitrogen, which resulted from my not having been able to prepare a sufficiently large quantity of the substance; and, moreover, it might not have been perfectly pure.

presence in the spleen is evidently independent of that which might exist in the blood retained by this organ after death. Is it that the spleen secretes cholesterine? This can only be determined by actual experiment; but it is very remarkable that a part of the blood which is supplied to the liver should come directly from an organ containing large quantities of a substance known to enter into the composition of the bile.

II. "Description of a Chronometer Compass." By RALPH REEDER, Esq., of Cincinnati, U. S. Communicated by Capt. WASHINGTON, R.N., F.R.S. Received Feb. 26,

1857.

This instrument is a combination of the Universal Dial and Chronometer, and is intended to show the errors of the magnetic needle, both at sea and on land, and, in clear weather, to perform in place of the needle.

III. Extract of a Letter addressed to General SABINE, R.A. Treas. and V.P.R.S., by M. R. WOLF, dated Zurich, March 7, 1857. Communicated by Gen. SABINE.

J'avais l'honneur de vous envoyer le 2me numéro de mes Mittheilungen über die Sonnenflecken,' dans lequel j'ai développé que mes observations des tâches du soleil dans les années 1849 à 1855 prouvent assez clairement, qu'il y a dans ces phénomènes curieux une période correspondante avec l'année terrestre, dont les deux minima correspondent aux deux époques où la terre passe par le plan contenant l'axe du soleil et une parallèle à l'axe de la terre,-les deux maxima aux deux époques où la terre s'éloigne le plus de ce plan. Depuis ce temps-là j'ai trouvé qu'il y a une période correspondante dans les variations du magnétisme terrestre. En combinant les variations en déclinaison observées sur l'hémisphère boréale avec celles de l'hémisphère australe, pour éliminer l'influence de la déclinaison du soleil, j'ai trouvé une période annuelle pour ces variations, dans laquelle les deux minima et le deux maxima se présentent encore plus claires que dans les tâches solaires, et de même encore plus rapprochés des

époques ci-dessus mentionées. Je crois que cette nouvelle correspondance entre les tâches solaires et le magnétisme terrestre, que j'avais déjà soupçonnée en 1853 (voir les Mittheil. der Nat. Ges. in Bern), suffira pour convaincre les derniers sceptiques qu'il y a une correspondance réelle entre ces deux phénomènes.

A peine avais-je terminé cette recherche et donné à l'Académie de Paris le même résumé que vous avez lû dans les dernières lignes et que j'aimerais voir communiqué par vous à la Société Royale, que je trouvai dans votre 3me mémoire sur les Magnetic Disturbances' la même période découverte par vous dans ces Disturbances.' Je suis bien heureux de vous rencontrer de nouveaux dans mes études, et je donnerai dans le 3me numéro de mes Mittheilungen,' qui paraîtra sous peu, et un extrait de votre lettre du 16 Décembre et la date de votre 3me mémoire.

IV. "Anatomical Description of a Species of Asteroid Polypes, probably forming the type of a new genus of Alcyonidæ." By JOHN DENIS MACDONALD, Assist. Surg. R.N. Communicated by Capt. DENHAM, F.R.S. Received January 13, 1857.

On leaving the Conway Reef (lat. 21° 44′ 48′′ S., long. 174° 37' 45" E.), July 4, 1855, a very beautiful branched asteroid Zoophyte, belonging to the Alcyonidæ, was brought up from a depth of between 30 and 40 fathoms, on the buoy-rope of the anchor.

The polypidom, from a trunk of about one inch and a half in diameter, branched off, with much irregularity, but generally in a dichotomous manner, into very minute subdivisions.

The investing membrane was strengthened by the close deposition of elongated, fusiform, and minutely tuberculated spicula of a deep crimson-lake tint, which impart their colour to the whole mass.

The internal substance was chiefly composed of longitudinal muscular septa, radiating from the central axis (which contained no denser material), frequently communicating with one another laterally, and being fixed into the internal surface of the integument in vertical lines. These muscular septa were invested on each side with a layer of finely reticulated vessels; both sets being connected by

numerous transverse trunks passing through the intervening muscular tissue, and the spaces between the septa were filled with a transparent glairy fluid.

The polyp-cells were exposed and solitary, resting on the internal surface of short branchlets strengthened by large dorsal spicula, one of which, much larger than the rest, extended considerably beyond the polyp-cells, tapering gently to a needle-like point. These latter spicula are covered with tubercles, and in every respect, but in size, similar to those of the general integument.

The small spicula on the internal or ventral surface of the branchlets diverge from one another in the peripheral direction, while those on the dorsal border are disposed longitudinally.

The mouth of each cup-like polyp-cell was surrounded with about eight projecting spicula, whose fixed extremities were curved upwards and inwards, festoon-fashion, while numerous smaller ones were so disposed as to fill up the open spaces posteriorly, and thus strengthen the body of the cell.

Although I have not been able to count the number of the oral tentacula satisfactorily, from their proportional size I can readily believe that there, were about eight in this species, as in most if not all other asteroid polypes. They were broad and flat, tapering to a blunt point, like those of Sarcodyction (Forbes), to which genus I have no doubt this Zoophyte is nearly allied, though the habit of the polypidom is so very different.

March 19, 1857.

Dr. W. A. MILLER, Vice-President, in the Chair.

The following communications were read :

I. "A System of Train-Signalling, by which also disabled Trains may telegraph for assistance without the aid of portable apparatus." By CHARLES V. WALKER, Esq., F.R.S. Received March 9, 1857.

(Abstract.)

When, in the early days of telegraphy, messages were sent and

trains were signalled on the same wires, no facilities existed for reducing the apparatus employed for the latter purpose, to a simple form. The case is now becoming different, special wires being largely devoted to train signals; hence the present system.

The instrument employed is a large electro-magnet, with a moveable armature, carrying a stem and a hammer, which latter strikes on a bell by the direct force of magnetism. It is provided with a contact-maker, a spring, the depression of which causes a current to circulate. The bobbins are 4 in. × 3 in.; and are filled with ten pounds of covered copper wire, No. 16 or No. 18. The core is of five-eight inch iron. The armature and appendages weigh 24 oz. Bells of this kind have been in action for five years without cleaning or repairing. The battery is zinc-graphite, and a solution of 1 sulph. ac. +8 or 10 water. The plates, 7 in. × 3 in., are placed in stone pots that contain about a quart, the zinc standing in a gutta-percha slipper, containing mercury. Batteries of this kind will do their work untended for half a year and longer.

The language consists of blows on the bell; the number of blows varies according to the train-signal to be given. The distinctions required for ordinary purposes being few, the bell-language is very appropriate, from its addressing the ear, from its simplicity and from the facility with which the signals are given and taken. One blow is for the starting of an ordinary train; two, for an express; three, for the arrival of a train; five, for stopping all trains; six, for testing. This is a general code; other forms of code are used for protecting level crossings and junctions; but the fundamental signals of the general code are of universal application. This system was introduced five years ago on the South Eastern Railway; and at the present time consists of about 100 bells, to which additions are in progress.

The bells are connected in pairs, both bells being in a circuit that terminates in the earth in the usual way, at each station. The signal is made by depressing the spring from its earth-contact, upon the zinc end of the battery, the graphite end being in permanent connexion with the earth. The battery being thus introduced between the bell and the earth, a current circulates along the wire and produces one blow upon the bell. The home bell may be excluded or not from the circuit, when a signal is sent.