These experiments consisted of the measurement of the moment transmitted, by fluid viscosity, across the annular space between two concentric cylinders, one of which revolves while the other is stationary. The fluid used in these experiments was water. Three distinct sets of conditions were tried, viz. :- (1) Outer cylinder revolving, inner cylinder stationary. (2) Inner cylinder revolving, outer cylinder stationary. (3) Repetition of series (1) with an annulus of different width.

No abstract

To sum up the chief points of the second paper :-(1) The rate of evolution or absorption of heat by quenched steel is, after a short initial period, approximately in inverse ratio to the time elapsed after quenching.(2) The actual rate of evolution has been determined for various specimens.(3) The rate of contraction of quenched steel was found to follow the same law as the rate Of evolution or absorption of heat.(4) This suggests that the contraction is intimately connected with the heat evolution, both being due to the same cause..

material, and the potassium chloride formed exercises its specific influence on this reaction.The secondary action upon potassium iodide producing iodine is practically an instantaneous one, unless the quantity of this substance is below a certain minimum. Below this the velocity observed in the mixture will be less than normal. The effect of increasing the amount of this substance to much greater than the minimum is closely analo gous to that of a similar increase of any neutral salt.The velocity is an exponential function of the temperature, as was observed in Messrs. Harcourt and Esson's investigations. As the latter increases in arithmetical progression, the former increases in geometrical progression. The rate is about doubled for a rise of 5° 0. The ratio in this progression is not, however, absolutely constant, but varies a little with the temperature at which it is taken. Thus between 0° and 15° C. the rate is a little more than doubled for a rise of 5° ; between 20° and 30° it is a little less than doubled. Communicated by Lord R a y l e i g h , Sec. R.S. Received November 30, 1888.The experiments here described, which were made during April and May of the present year (1888), to determine the constant of viscosity of water, may be of some interest on account of the newness of the method employed, and also as being on rather a larger scale than other experiments which have been made with the same object. Fig. 1 gives a section of the apparatus used. A and B are two coaxial cylinders; of these A is mounted on the vertical axis E, and can be made to rotate by a belt passing over the wheel F. B is suspended by a long fine wire C, and the annular space between A and B is filled with water or any other fluid to be experi mented on.A little way above the lower edge of B is fixed an air-tight dia phragm D, so that when the space between the two cylinders is filled with liquid air is inclosed under D, and the liquid touches B only on the cylindrical surface.The interior of B above D is filled with water which serves the purposes of checking the torsional vibrations of B, of preventing any rapid change of temperature of the liquid in the annulus, and of holding the thermometer.The experiments were made by driving the cylinder A at a uniform speed and recording the angle through which B is turned when it comes to rest under the action of the fluid friction on its cylindrical surface and the torsion of the suspending wire C. A was driven by 1888.]

The optical arrangement of the simple eyes of Vertebrates is well understood, but as regards the action of the composite eyes of Insects and Crustacea less certainty has hitherto prevailed. In the former class of eye a single lens, or its equivalent, forms an image on a concave retina, built up, as a sort of tesselated pavement, of the sensitive terminations of the fibres of the optic nerve, and, if the lens is perfect and the pupil large enough, the definition is limited by the distance apart of the nerve-terminations, for, in order that two objects may appear as two to the eye, they must subtend at least such an angle that their images as formed by the lens shall not fall on the same nerve-termination.