Report of the Kew Committee. 467 



for the purpose of purchasing a half-mile of double wire telegraphic 

 cable and reel, together with switches and keys, in order that the 

 two cameras may be worked at a distance of 800 yards apart. 



A stand has been erected on the roof of the Observatory, where 

 camera A will be permanently placed, and camera B will be similarly 

 supported by another permanent stand at the other end of the cable. 

 Both cameras being oriented with reference to the same point of the 

 horizon, the distant observer will be instructed as to the direction and 

 elevation of his instrument by means of a telephone switched on to 

 the line for the purpose. 



Some difficulties having been met with in working the electrical 

 instantaneous shutters, part of the apparatus was returned to the 

 makers, the Philosophical Instrument Construction Society, Cam- 

 bridge, and rectified. 



Experiments with the new arrangement are now being made, and 

 should they prove successful it is intended to bury the cable in the 

 ground across the park beside the Observatory gas main, thereby 

 obviating the present necessity of laying out and winding it in again 

 every time it is desirable to make cloud altitude and air-current 

 motion determinations. 



Solar Radiation Thermometers. The experiments with a view to 

 determining the causes of variation in the readings of similarly con- 

 structed and exposed black bulb thermometers, in vacuo, have been 

 continued during the year. 



The first series of observations having been concluded, and the 

 results communicated to the Royal Meteorological Society and pub- 

 lished in their " Quarterly Journal," vol. x, p. 45, the six thermo- 

 meters were returned to Messrs. Negretti and Zambra, in order that 

 all might have their bulbs coated with three coats of lampblack and 

 their jackets altered : one pair is now enclosed in small bulbs, a 

 second pair in medium, and the third pair in large bulbs. 



With the exception of one which was accidentally broken in July, 

 they have been read daily since May 3. The results have not yet 

 been fully discussed, but a cursory inspection appears to indicate that 

 the larger the containing bulb the lower is the reading of the enclosed 

 blackened bulb thermometer. 



Ventilation Experiments. Assistance has been given to a Sub-Com- 

 mittee of the Sanitary Institute in their experiments on the motion of 

 air in ventilating tubes, which have been carried on during the 

 summer under the charge of Mr. R. Rymer Jones, C.E., in a hut 

 erected for the purpose, adjacent to the Observatory. 



The experiments are in continuation of those prosecuted in the 

 Experimental House in 1880. 



Wind Integrator. At the request of Mr. Walter Baily, M.A., a wind- 

 component integrator of his invention, described in the " Phil. Mag.," 



