422 REPORT—1883. 
the needle at the solstices, and particularly the summer solstice, is at Kew and 
Toronto pushed to the east, while at Trevandrum and Bombay it is pushed to the 
west, as if the north induction system had become particularly powerful on these 
occasions. In conclusion, I wish to state that these remarks are introduced rather 
as denoting a method of grouping together the annual and semiannual observations 
than as embodying conclusions of a final nature. This working hypothesis may be 
summarised as follows :— 
(a) The sun’s polar influence on the earth’s magnetism is greatest at the 
solstices. 
(8) This effect is stronger at the June than at the December solstice. 
(y) It seems particularly to afiect what has been termed the induction magnetic 
system of the earth. 
7. Description of a Marine Anemometer. By Dr. 'W. G. Brack, F.R.M.S. 
This instrument is designed on the idea of registering the pressure of the wind 
on the sail of a ship for the purposes of the navigator. | 
__ It therefore consists of a hollow mast, carrying a square sail, suspended from a 
fixed yard at the head, and having a free foot stretched on another yard below. 
The tube of the mast contains a spiral spring at the upper half, with a pointer 
outside, and from this proceeds the sheet or a cord, going under a pulley at the 
lower end, to be attached to the lower yard of the sail. 
The heel of the mast can be secured by suitable plinth and screw, and placed 
on a railing or other likely structure on the bridge of the ship or steamer, 
A movable vane surmounts the head of the mast, and the sail can be turned by 
hand to face the full direction of the wind, and the pressure on the sail can then ° 
be read off on the scale on the side. This scale is marked in inches and pounds 
and their parts, temporarily in the ratio of one inch to four pounds. 
Estimation of the true direction of the wind and its velocity and force can thus 
be obtained by constructing a diagram of parallelogram of forces of the wind and 
rate of sailing. The diagonal would he furnished by the perpendicular line to the ~ 
face of the sail pointing to the apparent wind, and the required angle would be 
read off from the dial of degrees marked on the circumference of the lower plinth. 
8. Ona Method for Measuring the Height of the Clouds. 
By Professor Luroru. 
This method simply consists of taking a strong electric lamp, together with a 
reflector and a tube, and directing a pencil ot luminous rays, say vertically, 
against the sky. These rays will produce within the cloud that occupies the 
zenith a luminous spot, and it is only needful to determine the angular elevation 
of that spot above the horizon from a distant point, whose position with respect to 
the lamp is known; hence the calculation of the height in question will be but one 
of the simplest tasks in plane trigonometry. The method will of course best be 
applicable during night, but it might also be used by daylight, if the sunshine is 
not too bright. Still there might be limits as to the height for measuring which 
the method is capable of being adapted. 
9. On Fixing a Standard of White Light. By Caprain Abney, F.R.S. 
The author described an instrument which he had devised nine years ago, and 
had used for comparison of the electric light and gas-light when serving on a 
Government Committee. The comparison of incandescence light proved to be 
highly instructive; and eventually it was found that for obtaining a standard light 
of high temperature, nothing could be better except the crater of the positive pole 
of the electric arc. This latter has invariably the same temperature, as was shown 
by the author and Colonel Festing in a paper which has recently appeared in the 
Proceedings of the Royal Society. It has, however, one insuperable drawback as 
a 
