292 Mr, GoMingha7)i'sJlep(yr^,.'A\.. [Oct. 



should now be gently stopped, by putting the hands at the sides 

 of tiie weight, and a new set of experiments commenced as 

 above ; perhaps eight sets, four in the morning, and four in the 

 afternoon, may be taken in a day : the names of the observers 

 to be noted ; and each person's observations to be kept distinct. 

 The forenoon sets being done, screw up the Ys, so that the 

 Icnife-edges may rest on them ; Hft the penduUun gently up, and 

 wipe the knife*edges with the oiled cloth or flannel, and place it 

 again with great care in the Ys, covering the whole with a cloth 

 to keep ofFdust and damp. Before the afternoon's observations, 

 wipe the knife-edges, and lower them upon the agates very 

 carefully ; should there not be light enough in the Observatory- 

 tent, the top may be opened ; but great care should be taken to 

 exclude wind from the pendulum during the time of making the 

 experiments ; on this account, the face of the pillar and the 

 opening are placed on the side opposite to the prevailing wind. 

 • " Three distinct sets of observations, of 120 or 130 observations 

 in each set, should be taken if possible. The frame with the 

 agates to be examined and levelled between each set, and the 

 other points of adjustment also to be examined. 



" During the time of making the experiments, the rate of the 

 clock must be correctly ascertained, both by the stars and the 

 sun, and all the observations carefully registered. A small 

 pillar may be built for the transit instrument, sufficiently to the 

 right in the Observatory, not to obstruct the view of the pendu-« 

 lum through the telescope, but so as to take advantage of the 

 opening in the top of the Observatory for taking the transits. 



" Meridian altitudes of the sun, if not too high for the artificial 

 horizon, and of stars on each side of the zenith, should be 

 observed ; the more numerous these observations are the better, 

 as a result to the nearest second is required. 



" The longitudes must be found by the chronometers, and 

 eclipsesof the satellites of Jupiter. 



" The nearer the place of observation is to the sea the better ; 



the height of the pendulum above the sea must be found by 

 levelling ; also the rise and fall of the tide ; the time of high 

 water on full and change ; the variation of the compass ; the 

 bearings and distances of the different mountains, the extent 

 and elevation nearly, and if known, to note what they are com- 

 posed of; also the bearings and distances of islands, and parts 

 of the coast ; and particularly the nature of the soil, of the place 

 on which the experiments are made ; whether sandy, or mould, 

 or rocky ; if either of the two former, whether to any depth. 



" Every opportunity is to be taken for finding the bearings and 

 distances of places and points along the coasts which may be iu 

 sight, with the difference of latitude and difference of longitude; 

 also for obtaining soundings, as well as the set of the currents, 

 aa shown by the chronometers and meridian observations, to 



