While the theory of stereo-isomerism has been employed in the case of many carbon compounds, it has had but few applications in that of organic substances containing nitrogen. Its use has been almost confined to explaining the occurrence of isomers among the oximes. The addition of a new member to the small list of four or five pairs of hydrazones, whose isomerism can be explained only on the assumption of diversity in the disposition of the atoms in space, is therefore not unwelcome as giving additional weight to the theory.

Since the occlusion of hydrogen and carbonic oxide by palladium and iron was first discovered by Graham, many similar effects have been discovered. Prof. Knott has investigated in considerable detail the very peculiar changes in the thermo-electric position and in the electrical resistance of palladium when variously charged with hydrogen. With respect to iron, Dr Monckman has experimented on the resistance of iron occluding carbonic oxide, but, in regard to hydrogen, he came to the conclusion that no change in the thermo-electric properties could be detected.

The first obvious difficulty which presents itself, in trying to derive Clerk-Maxwell's equations from those of the elastic-solid theory, appears in the fact that the latter, being linear, do not impose any relations among simultaneous disturbances. Thus, for instance, they indicate no reason for the associated disturbances which, in Maxwell's theory, constitute a ray of polarised light. Hence it appears that we must look on the vectors of electric and magnetic force, if they are to be accounted for on ordinary dynamical principles, as being necessary concomitants, qualities, or characteristics of one and the same vector-disturbance of the ether, and not themselves primarily disturbances. From this point of view the disturbance, in itself, does not correspond to light, and may perhaps not affect any of our senses. And the very form of the elastic equation at once suggests any number of sets of two concomitants of the desired nature, which are found to be related to one another in the way required by Maxwell's equations.

However far back written records conduct us in an investigation of the early history of mankind, it can no longer be maintained that they cover but a small portion of man's existence on the globe. That human racial characters were broadly marked, some 6000 years ago, has been surmised from an analysis of the ancient wall paintings of Egypt. Thus, in the tombs of the kings at Thebes are to be seen, to this day, coloured and highly expressive portraits of the four principal races who then frequented the Nile valley; and it is a remarkable fact that their distinguishing peculiarities, as depicted in the conventional eye and reddish-brown colour of the Egyptian, the fair-skinned and blue-eyed Lybian, the aquiline profile of the Semite, and the thick lip and curly hair of the Negro, are equally descriptive of their modern representatives.

The recent publication of the full results of Amagat's magnificent experiments has led me to make further comparisons with the empirical formula (originally suggested by the graphs of my Challenger work) which I have on several occasions brought before the Society:—viz.

While making physical observations during some recent cruises on board H.M.S. “Jackal,” I was on several occasions made to feel the want of a water-bottle which could be relied on to act with precision in rough weather. Mill's slip water-bottle, which leaves nothing to be desired in its working in smooth water, at least up to depths of 400 or 500 fathoms, is apt to be closed prematurely by the jerk on the sounding line when the ship is rolling or pitching in a sea-way; and considerable doubt arises as to the point from which samples are really obtained.

Some years ago, in an investigation on the affinity of organic bases, I was led to study the amount of decomposition suffered by various salts when dissolved in water, for a knowledge of this amount gives us a method of comparing the relative strengths of weak bases. When these bases are made to unite with a given acid, the extent to which the resulting salts are decomposed, in equivalent aqueous solutions, into acid and base, depends directly on the strength of the various bases. The same process of decomposition by water, or hydrolysis, can also be made use of to determine the strengths of weak acids, and experiments in this direction have been executed by Lellmann and his pupils, and by Shields. As the amount of free acid or free base in a hydrolysed solution cannot be determined directly by neutralisation, on account of the progressive disturbance of the chemical equilibrium involved in the process, it must be determined by taking advantage of some property of the acid or base which is susceptible of accurate measurement, and does not destroy the chemical equilibrium, or else does so in a manner amenable to calculation.

The following account nf the pallial complex of the Tectibranch Dolabella is, as regards the minuter details, founded on a single specimen (Dolabella rumphii) kindly sent me by Professor M'Intosh of St Andrews. By an examination of the collection in the South Kensington Natural History Museum I was enabled to verify for the genus points which might have been peculiar to this species, and in one point to note an important variation.

A few words as to the necessity of an accurate description of the pallial complex or system of organs in the mantle cavity of the Opisthobranchiata, and the inferences that may be drawn, may not be out of place.

It is contended that Quaternions (as a method) are more comprehensive and less artificial than—and, in fact, in every way far superior to—Coordinates. Thus Professor Tait, in the Preface to his Elementary Treatise of Quaternions (1867), reproduced in the second and third editions (1873 and 1890), writes—“It must always be remembered that Cartesian methods are mere particular cases of quaternions where most of the distinctive features have disappeared; and that when, in the treatment of any particular question, scalars have to be adopted, the quaternion solution becomes identical with the Cartesian one. Nothing, therefore, is ever lost, though much is generally gained, by employing quaternions in place of ordinary methods. In fact, even when quaternions degrade to scalars, they give the solution of the most general statement of the problem they are applied to, quite independent of any limitations as to choice of particular coordinate axes.”

My title is purposely ambiguous, because it has to represent two things—I intend to treat not only of what a quaternion really is, but also of its self-containedness, or independence.

Professor Cayley has just stated that “while co-ordinates are applicable to the whole science of geometry, and are the natural and appropriate basis and method in the science, Quaternions seem to me a particular and very artificial method for treating such parts of the science of three-dimensional Geometry as are most naturally discussed by means of the rectangular co-ordinates x, y, z.”

In a paper, read for me to the Society in January last (ante, p. 245), I pointed out the difficulties I had met with in trying to reconcile Van der Waals' equation with Amagat's experimental data for common liquids, and I promised to recur to the question when the state of my health should permit. I now find that, as I had then only surmised, the constants in Van der Waals' equation necessarily become non-real when we try to adjust it to Amagat's data.

This paper is a continuation of a paper communicated to the Society in July of last year, the publication of which was withheld until the whole subject could be treated as one. In the previous paper we discussed the magnetic induction in Iron and Steel Tubes. These tubes, and the nickel tubes now under discussion, were constructed primarily for the purpose of investigating their changes of volume under magnetisation ; but it seemed advisable to study as. many of their magnetic properties as possible.

In the note which recorded the first observation of the volume effects of magnetisation, the nickel tube experimented with was formed by rolling up a sheet of ordinary commercial nickel to the convenient size.

We are now able to record the preliminary results obtained with the nickel tubes described in the preceding Note on Magnetic Induction. Broadly speaking, the behaviour of the nickel resembles the behaviour of certain of the Iron Tubes as described in previous communications.

The vertices of the original triangle being

the conic being

and A1, B1, C1,. … being defined by the nine equations

The problem in question with its solution appeared in the Cambridge Mathematical Journal, vol. ii. pp. 232–236, being given by Sylvester to show how his recently discovered “dialytic” method might be applied to ternary quadratics.

I in part reproduce this very interesting paper for the sake of a remark which appears to me important. I write (a, b, c, f, g, h) in place of Muir's (A, B, C, A′, B′, C′), and take as usual (A, B, C, F, G, H) and K to denote (bc − f2, ca − g2, ab − h2, gh − af, hf − bg, fg − ch) and the discriminant abc − af2 − bg2 − ch2 + 2fgh.

During the last two winters I have had considerable opportunity of making observations on the reproduction of the edible crabs of the Northumberland coast; and though, my results are still incomplete, and some of them, as, for instance, those relating to the size of sexually mature crabs, are chiefly of local importance, I think the meagreness of past work on the subject, and its practical importance in connection with fishery legislation, justify me in publishing some account of what I have seen.

The question as to the perfect uniformity or otherwise of the chemical composition of sea-water is one of great difficulty and complexity. It is quite certain that, broadly speaking, great differences do not exist, so that a conclusion can only be arrived at by the application of methods of analysis of great refinement, and then only if the limits of experimental error inherent in these methods be satisfactorily determined.

If we take the set of equations

the eliminant of which is

and from the 1st, 2nd, and 3rd eliminate xyw and xyz, from the 2nd, 3rd, and 4th eliminate xyz and yzw, from the 3rd, 4th, and 1st eliminate yzw and xzw, and from the 4th, 1st, and 2nd eliminate xzw and xyw, we obtain the set

the eliminant of which is clearly

Sensori-motor reaction time is the interval that elapses between the stimulation of a sense organ and a motor response. The physiological process involved consists of (a) an afferent factor,—the stimulation of a sensory terminal, and transmission of an impulse along sensory nerve fibres to the brain; (b) a psychical factor, involving an act of sensory perception and the voluntary production of a motor impulse; (c) an efferent factor,—the transmission of an impulse along motor nerve fibres, and consequent contraction of muscle.