396 SURVEY OF THE COAST 



be brought lo approach as near to it as possible. It will 

 show that !io idleness is adniitted, as the omission or loss of 

 the points here mentioned would occasion an encroachment 

 upon the next day, or perhaps its recovering be long imped- 

 ed by circumstances, I suppose the observer to be furnish- 

 ed with at least one instrument for vertical angles, and one 

 for horizontal angles, time pieces, a barometer, tiiermometer, 

 sextant, and artificial horizon. 



The observer must be at his instruments one hour before 

 sunrise, to test their solid standing, clean them with a feather 

 from sandy dust, which is so often introduced by the wind 

 into the open axes, and upon the limbs, ^'c. If they need 

 any oil in the open axes, merely passing over the finger is 

 surtlcient. He must level the instruments and verify all ad- 

 justments; adjust the collimation line and the focus of the 

 telescopes and the reading microscopes, to clear vision, and 

 complete freedom from parallaxes, and verify the value of 

 their reading. For all this, the quiet state of the atmosphere, 

 and the coolness of the morning, with the full light which 

 precedes the rising of tlie sun, furnish the most favourable 

 circumstances. His instrument must necessarily be in good 

 order, and need very little of all these adjustments, ^'c. if he 

 shall be ready about sunrise, as he should ; and this will be 

 the case, if he has devoted the proper attentions at the begin- 

 ning of the stafion. 



Then he will level his instrument finally, and the rising of 

 the sun will the proper moment to observe the angles upon 

 the signals, within about 40° on each side of the southern 

 meridian, until such time as the sun is about its double dia- 

 meter above the horizon in case of a southern declination, 

 or on the six o'clock meridian wlien in a northern declina- 

 tion ; at which time it is proper to take one or two azi;uuths 

 of the sun, in the manner indicated at the proper place. 



These azimuths must be followed immediately by obser- 

 vations of zenith distances or altitudes of the sun, for the de- 

 termination of the time, which it is necessary to liave as fiee 

 from the rate of the chronometer as possible, and which 



