C iy) 
of 1877, and after the cleaning and removal of 1898) to a new 
investigation which had to embrace the whole of these periods. The 
results of this investigation are given in the present paper. 
I have confined myself to such results as could be derived from 
the mean daily rates during periods of about a month. Thus it was 
not necessary that the time-determinations on which the investigation 
is based were discussed with the utmost accuracy. In this way I inves- 
tigated successively the three periods, 1877—1898, 1862—1874 
and 1899—1902. The results for these three periods will be com- 
munieated in this order. Then the observed amplitudes of the period 
1877—1898 will be investigated, so far as their yearly periodicity 
is concerned, and finally the several results will be compared with 
each other. 
As a consequence of the restriction of the investigation to the 
monthly means, the question is considered from one point of view 
only. In the mean time however Mr. Wreper has definitively discussed 
all the time-determinations from 1882—1898, and has undertaken 
investigations about the rates of the clock during shorter periods. 
It is to be expected that, when these investigations will be completed, 
the comparison of his results with mine will also throw more light 
on the phenomenon which is here treated. 
Very recently, while my investigation was already nearly com- 
pleted, I had occasion more closely to study the computations which 
Kaiser made about the clock Honwi 17 during the last years of his 
life, and which are preserved in manuscript at the observatory. | 
then found that as early as 1870 his attention had been drawn to 
this particular yearly inequality as to a remarkable phenome- 
non. Among the papers I found a summary of monthly means 
of rates, corrected for barometer and temperature, from which mean 
results had been formed by combining the corresponding months of 
the years 1862—1870. These means show clearly a periodicity having 
its maxima in May and October, and a total amplitude of 0°.09. 
Further I found means for the half-years February—July and August— 
January for each of the years 1863 to 1870. The differences between 
the two half-years vary between + 0.°026 and + 0.8048 and Kaiser 
adds the remark that the only difference between the two half-years is 
that in one of them the temperature is, in the mean, rising, while 
in the other it is falling. 
I. The period 1877—1898. 
3 The eloek-rates which were taken as the basis of the inves- 
tigation were, for the period 1877—March 1882, derived from the 
