Report of the Keio Observatory Committee. 



345 



able; the range was beyond the limits of the instrument to record defi- 

 nitely, but the maximum exceeded 11 seconds of arc. 



During November the action of the boom became sluggish, and 

 the records for some time were doubtful. It was ultimately found, 

 after consultation Avith Professor Milne, that a part of the edge of 

 the agate cup resting on the pivot was scratched and jagged. This 

 •defect was remedied by moving the weight and tie piece round through 

 45°, and so bringing a different part of the agate cup on to the pivot. 

 The general working has since been satisfactory. 



The remarks made in last year's ' Eeport ' as to the uncertainty of 

 the time measurements still hold good, and no attempt is made to 

 give these values to nearer than 0*1 minute. 



A detailed list of the movements recorded from April, 1898, to 

 March, 1899, was made and sent to Professor Milne, and will be found 

 in the ' Eeport' of the British Association for 1899, " Seismological 

 Investigations Committee's Report." 



It is proposed to tabulate the disturbances for the remainder of 

 1899 in a similar manner. 



IV. Experimental Work. 



Fo(j and Mist. — The observations of a series of distant objects, 

 referred to in previous ' Reports,' have been continued. A note is taken 

 of the most distant of the selected objects which is visible at each 

 •observation hour. 



Atmospheric Electricity. — The comparisons of the potential, at the 

 point where the jet from the water-dropper breaks up, and at a fixed 

 station on the Observatory lawn, referred to in last year's ' Report,' 

 have been continued, and the observations have been taken three or 

 four times every month. 



Platinum Thermometry. — The results of the comparison of platinum 

 ^nd gas thermometers at Sevres, referred to in last year's ' Report,' 

 were worked up by Dr. Chappuis and Dr. Marker, and embodied in a 

 paper which was read before the Royal Society in June and will appear 

 in the ' Philosophical Transactions.' 



The experiments which were begun in 1895 into the constancy and 

 general behaviour of platinum thermometers have led to the accumu- 

 lation of a large number of results. These have been dealt with by 

 the Superintendent in a critical paper, which was recently read before 

 the Royal Society. 



Towards the end of the year an oil-bath was constructed, from the 

 designs mainly of Dr. Harker, for the purpose of comparing thermo- 

 meters at high temperatures. Some preliminary comparisons have 

 already been made in it of a few German and English mercury 

 standards with a platinum thermometer. 



