1821.] Capt. Pony's Voyage. 69 



1. The arc of intercepted latitude was greater than between 

 any two of the stations of 1818 ; the possible errors of observa- 

 tion have consequently had a less influence on the accuracy of 

 the deductions. 



2. The employment of two clocks afforded a means of procur- 

 ing double and corresponding results. Indeed as it happened 

 fortunately that each pendulum would fit into either clock, four 

 corresponding results were obtained for the acceleration between 

 London and Melville Island. 



3. The number of vibrations made by the clocks in London 

 was ascertained by two distinct series of experiments, one 

 before the departure, and a second after the return of the expe- 

 dition ; the very near agreement of the results on these occa- 

 sions proving that neither of the clocks, nor any part of their 

 apparatus, had sustained any injury during the voyage, affecting 

 their rate of going ; as well as affording a satisfactory inference 

 of the confidence which is due to this mode of experiment ; the 

 number of vibrations in 24 hours in London was as follows : 



Vibrations in a mean solar day. 



r , , , /January, 1819 86392-56731 QfiQno .„„ 



Clock 1. | Decea / b ' er> 1820 86 3 92 . 335 3 ) 86392-4513 



n rt ,.L.*o /March, 1819 86496-997 1 QP/inr nQ ,,- 



Clock 2. | Decem ' berj 1820 86496-9741 ) §6496-9855 



4. From the time which was allowed for the experiments at 

 Melville Island being fully sufficient for their completion, the 

 rate of each clock being determined by a mean of 85 intervals of 

 24 hours each. 



And, lastly, from the correspondence in the results obtained 

 by the two clocks ; the daily acceleration of the one, on a mean 

 of the experiments with both pendulums, being 74-8151 vibra- 

 tions, and by the other, 74-6528 vibrations. The mean of the 

 two, therefore, 74-734, is considered as the true acceleration of 

 a pendulum between the latitudes of 51° 31' 08" 4'" and 

 74° 47' 14" 36'" N. 



By comparing, in a similar manner, the experiments made in 

 tlie voyage of 1818 with each other, the acceleration of the pen- 

 dulum between the several stations at which it was tried, has 

 been obtained as follows : 



Vibrations in a mean solar day. 



Between London and Brassa 33-107 



London and Hare Island 65-2386 



Brassa and Hare Island 32-1316 



The following table contains the deductions which have been 

 obtained by calculation from these several results : 



