160 REPORT — 1894, 



observed, though a slight change of position appears to take place during 

 the time of observation, owing possibly to the presence of the observer or 

 the heat of the lamp. This change, however, is very slight, and the 

 mean of the eleven observations of each set is taken as showing the 

 position of the mirror for that day at Paris noon. These mean scale 

 readings have been laid on a curve with the date as one argument and 

 the divisions of the scale as the other. The result shows that the mirror 

 has been constantly turning in azimuth from the east towards the north 

 during the whole period over which the observations have extended 

 (May 26 to July 31). The total amount of this movement has been 

 517 mm. on the scale in sixty-six days, or an angular rotation of 9° 37' 23" 

 for the ray falling on the mirror from the lamp ; which is, of course, 

 equivalent to an angular rotation of 4° 48' 42" in the mirror itself. 



If, now, 20 mm. (^2"*016) be taken as the sensitiveness of the instru- 

 ment over all this time — though about this number there is some uncer- 

 tainty — the total tilt of the instrument towards the north appears to have 

 been fifty-two seconds of arc in sixty-six days. The stability of the nadir- 

 point of the mural circle in the adjoining observatory proves that this tilt 

 must either be in the superficial layer of the rock to which the instrument 

 is attached or, which is far more probable, in the pendulum itself. 



The experiments confirm the results obtained elsewhei'e, that the 

 instrument, while unfitted to show the slower progressive tilts of the 

 earth's surface, is pre-eminently suited, by its great sensitiveness and 

 momentary stability, for the indication of earth tremors. However, to 

 bring out the full powers of the apparatus it is obviously necessary to 

 secure a continuous photographic record of the position of the mirror. 



M. Antoine d'Abbadie, at whose cost the pendulum was supplied, has 

 caused simultaneous observations to be taken with his ' nadirane ' at 

 Abbadia in north latitude 43° 22''8 and longitude 7m. Os. west of Green- 

 wich. The readings at the two stations have, however, not yet been com- 

 pared. 



The Electrolytic Methods of Qxiantitative Analysis. — Report of the 

 Committee, consisting] of Professor J, Emerson Reynolds (Chair- 

 man), Dr. C. A. KoHN (Secretary), Professor P. Frankland, 

 Professor F. Clowes, Dr. Hugh Marshall, Mr. A. E. Fletcher, 

 Mr, D. H. Nagel, Mr. T, Turner, and Mr, J. B. Coleman, 



The first work undertaken by the Committee has been the compilation 

 of the bibliography of the subject, with which some progress has been 

 made. 



In addition, the plan on which the experimental part of the work is 

 to be carried out has been arranged. This is to include the investigation 

 of the methods for the determination of the following metals : silver, 

 lead, mercury, bismuth, cadmium, tin, antimony, iron, zinc, manganese ; 

 and subsequently of the methods for the separation of these metals both 

 from one another and from other metals. 



This is all the Committee undertook to do when they were appointed 

 without a grant of money. 



They now ask to be reappointed and with a grant of 40^. 



