42 



RECORD AND RESULTS OP 



If we combine the values of AT for October 1 and October 2, viz : — d*" 51" 33'.0, 

 — 4*" 49" 03". 8, — i*" 49" 26'. 5 respectively, also the values for October 9 and 

 October 10, viz: —4" 50" 49^5, —4'^ 49" 10'. 5, —4'^ 49" 30'.3 respectively, we 

 deduce the following table of daily rates : — 



1860. 

 1860. 

 1860. 

 1860. 

 1860. 



Daily rate of mean time chronometers. 



September 22, n*" chronometer time 



October 2, 3 



October 10, 3 " " 



October 1"?, 14 



October 31, 13 " " 



2007 



1062 



+ 2^64 



+ 0».88 



+ 5.44 



—0.84 



+ 1.88 



+ 0.45 



+ 0.U 



—1.04 



740 



+ 0^86 

 —0.41 

 + 0.52 

 —0.70 



PENDULUM EXPERIMENTS AT PORT FOULKE. 

 Explanatory Remarha and Record of Ohservations. 



The pendulum was swung at the Port Foulke Observatory on the same knife 

 edges as at Cambridge, the experiments extending over fourteen days between 

 September 26th and October 12th, 1860. These observations were made by Mr, 

 August Sonntag, assisted by Mr. H. RadclifF. The initial letters of the observer's 

 name are attached to each set of experiments. The following information is taken 

 from notes made by Mr. Sonntag. • " From a preliminary set of observations on the 

 morning of September 26th, it was found that at a temperature of 22° Fah. the 

 pendulum made very nearly 3607 vibrations in 3600 seconds of the pocket 

 chronometer. 



The time was noted when the swinging knife-edge passed the zero of the gradu- 

 ated arc. The pendulum being at rest, this zero appeared 0°.05 to the right (in an 

 inverting telescope) of the point of the knife-edge, producing a small difference in 

 the intervals when the pendulum was swinging from left to right and when swing- 

 ing in the opposite direction ; the mean of the intervals, however, is not affected 

 thereby. 



The observations were always commenced with a set marked 'Left,' the pendu- 

 lum when seen through the inverting telescope appearing to swing from left to 

 right ; immediately after a set is taken with the pendulum appearing in the opposite 

 direction marked ' Right.' Each set consists generally of eleven observations at 

 intervals of ten seconds, the mean is given at the bottom. The times are recorded 

 by means of the pocket chronometer. The semi-arcs are recorded, counted from 

 the middle either way. The azimuth of the plane of vibration was nearly N. W. 

 and S. E." 



The following description of the Observatory was received from Dr. Hayes : The 

 Port Foulke Observatory was a small frame structure, eight feet square, by seven 

 feet high in the centre, the roof pitching only one way. It was covered on the 

 outside with canvas, and was lined internally with bear, seal, and other skins. To 

 give greater warmth and solidity the snow was, during the winter, banked up 

 around it, covering it almost completely. It was erected on the first of a series of 

 terraces which lay northeast from the anchorage, and its foundation was thirty-eight 

 feet above the mean tidal level. The rock on which it stood was primitive (a dark 

 reddish-brown syenite), which rose on either side of the harbor into hills from six 



