257 
1 879 .] Proceedings of Societies . 
Observatories of Kew and Trevandrum.” By Balfour Stewart, 
F.R.S., Professor of Natural Philosophy in Owens College, 
Manchester, and Morisabro Hiraoka. In a previous paper by 
one of the authors a table is given exhibiting monthly means of 
the Kew diurnal declination-range, corresponding to forty-eight 
points in each year, or four for each month, that is to say, 
approximately one every week ; and, in another paper, another 
similar table exhibits monthly means of the Trevandrum diurnal 
declination-range for weekly points. In the present paper these 
two tables are compared together. A comparison of the curves 
appears to lead to the following conclusions : — 
(1.) Generally speaking, maximum points or risings in the one 
curve must be associated with maximum points or risings in the 
other, rather than with minimum points or depressions. Indeed, 
the researches of Broun and others, from a different point of 
view, strengthen this conclusion, which is, moreover, abundantly 
supported by a glance at the curves themselves ; 
(2.) The oscillations of the Trevandrum curve are greater 
than those of the Kew curve ; 
(3.) In many cases where there is a want of striking likeness 
between the oscillations of the two curves, there are yet notice- 
able traces in the one curve corresponding to the oscillations of 
the other. There are, however, a few cases where there is a 
want of apparent likeness. 
(4.) In general, though not invariably, the oscillations of the 
Trevandrum curve follow rather than precede the corresponding 
oscillations of the Kew curve. 
“ On the Determination of the Rate of Vibration of 
Tuning Forks,” by Herbert McLeod, F.C.S., and George 
Sydenham Clarke, Lieut. R.E. The paper commences with a 
description of the time-measurer adopted. The tuning-fork ap- 
paratus consists of a brass drum resting on fridlion wheels, and 
driven by a weight and train. Uniformity of motion being of 
great importance, an air-regulator, consisting of a fan enclosed 
in the lower compartment of a cylindrical box, is employed. 
Round one end of the drum are wrapped strips of paper on which 
white equidistant lines have been so ruled that they are parallel 
to the axis of the drum when the strips are in position. The 
strip most frequently used has 486 lines round the complete cir- 
cumference of the drum. Opposite this graduated strip is placed 
a microscope with its axis horizontal. In the sub-stage is placed 
a 2" objective, producing an image of the graduations at the 
focus of the objecft-glass of the instrument. At the common 
focus of the two lenses is placed the tuning-fork, the stem of 
which is held vertical in a vice. If when the fork is in vibration 
the drum is made to rotate with such a velocity that one of the 
graduations passes over the interval between two adjacent gra- 
duations in the time of one vibration of the fork, a stationary 
VOL. IX. (N.S.) 
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