.j66 Analysis of Scientific Books. 



Towards the end of April the sun had influence to keep the therniometer 

 a few degrees above zero for some hours of the day. The clocks were now 

 unpacked and set up : the flooring being removed, the legs of the stands 

 were placed on slippers sunk some inches into the frozen ground in grooves 

 which were excavated by crow bars. 



It may be worthy of remark, that when the boxes containing the ther- 

 mometers which accompany the clocks were opened, the mercury was ob- 

 served to be retired into the bulbs and freezing, although tlie temperature 

 of the air had not been so low as the frozen ])oint of mercury for several 

 weeks. The thermometer boxes were enclosed each with the pendulum to 

 to which it belonged, in a stout case of oak ; and tliesc again were contained 

 in chests holding each one clock with its apparatus complete. Thether-" 

 mometers had been thoroughly cooled in their cases by the long continued 

 severity of the winter ; but the warmth had not yet made its way through 

 such a multiplicity of enclosures. It may be also mentioned, in proof of 

 the slowness with which such a mass of solid brass as constituted the bob 

 of the pendulums conforms to the temperature of the surrounding atmo- 

 sphere, compared with the mercury in the thermometer tubes, that several 

 hours had elapsed, after the jiendulums were taken out of their cases, 

 (when it is presumed they also may have been at —40°) before they ceased 

 to cause a deposit of moisture from the air of the room, which was about 

 the same number of degrees above zero : the mercury in the thermometers, 

 on the other hand, took up the temperature of the room within half an 

 hour after their exposure. The clocks were put in motion on the 30th of 

 April, and the account taken up on the 4th of May, the room having been 

 kept at about the temperature of + 45° for the preceding three days and 

 nights. 



It was not, however, till the third week in May that the wea- 

 ther became warm enough to commence the observations, for 

 during the first fortnight strong westerly winds prevailed, and 

 the observatory was occasionally buried in the drifted snow, when 

 the only access to it was by digging down to the window of 

 the room containing the clocks, and its mean temperature was 

 only 6°, instead of the desirable one of 45°, at which the expe- 

 riments in London had been conducted. During the second 

 fortnight the mean temperature was 25°; but various difficulties 

 occurred, and at the end of the month the thaw prevailed to such 

 an e.vtent as to oblige the abandonment of the house, before 

 any satisfactory results had been obtained. 



Towards the middle of June, therefore, the clocks were set 

 up in a tent, which could be occasionally heated by a stove, 

 and an account of their going is given from the 30th of June 

 to the 14th of July, when it was conceived that a sufficient 

 number of results had been obtained. 



From the observations, fully detailed in this paper, respecting 

 the length of the seconds' pendulum at the several places of 

 observations, it appears that its length at London being, as 

 ascertained by Captain Kater, =39.13929 inches, at Brassa it 

 is 39.16929 inches, at Hare Island 39.1984 inches, and at Mel- 

 ville Island 39.207 inches. 



Captain Sabine concludes this important communication 

 with the following table, shewing the diminution of gravity from 

 the pole to the equator, and the resulting ellipticity of the 



