1826.] of the Length of the Pendalam at the Equator, 293 



lay the foundation for a nautical survey, and for the improve- 

 ment of nautical science ; the variation of the compass should 

 also be found as often as possible ; the log-line should be accu-. 

 rately marked, so as to give correct distances for bases, and 

 for finding the strength of the currents. 



" The details of all the observations, experiments, and results,, 

 to be sent to the Observatory, to Mr. Goldingham the astro- 

 nomer, by every opportunity. 



" Journals noting every circumstance that may be thought 

 useful or interesting should be kept : both Robinson and Law- 

 rence may each also be directed to keep a journal. 



" Memora7idum of the Points to be attended to. 



"The frame vi^ith the agates to be accurately levelled. In 

 taking the pendulum of experiment out of the case, the greatest 

 care should be observed not to bend it ; the knife-edges to be 

 wiped with an oiled cloth at the beginning and at the end of the 

 experiments ; the knife-edges always to rest in the Ys, when the 

 pendulum is not in use, but to be let down on the agates 

 previously to making the observations. 



" The point of the pendulum of experiment not to be placed 

 beyond 1*35 on the arc of vibration before the pendulum is set 

 going ; so that the arc of vibration at the first time may not be 

 much more, nor much less, than 1*3. 



" The clock to be firmly secured, and quite upright: the frame 

 for suspending the pendulum of experiment also to be firmly 

 secured ; marks have been made by means of the arc on the 

 back of the clock-case to show the position the pendulum ought 

 to be brought to. 



*' Should the clock go too slow, screw up, or shorten j the pen- 

 dulum as many divisions of the nut at the bottom of it as the 

 clock loses seconds in 24 hours.* Should it go too fast, 

 lengthen the pendulum, as above, by means of the nut. 



" The clock to be wound up once a week. 



'' The chronometers to be wound up at the same hour every 

 day; one person to be specially appointed to do this. 



" In finding the latitude, take stars on each side of the zenith. 



" Equal altitudes the best mode of finding the time, though in 

 uncertain weather, it will be as well to take single altitudes also, 

 before nine o'clock, a. m. or after three, p. m. 



" On the days of experiment, it is absolutely necessary to have 

 the rate of the clock; this may be found both by the sun, and 

 with the transit instrument by the stars. 



" In taking bearings on ship board, use the azimuth compass: 

 allow for currents in making a base of the ship's run by the log 

 for a given time. 



• The value of these divisions is not exactly a sepond, perhaps j but it will b« foun4 

 9i\ex two ox three trials. 



