1774'» ROUND THE WORLD. 93 



ments, and with the sun and stars, or both sides of 

 the moon. By this last method, the errors which 

 may be either in the instruments or lunar tables, 

 destroy one another, and likewise those which may 

 arise from the observer himself; for some men may 

 observe closer than others. It' we consider the 

 number of observations that may be obtained in the 

 course of a month (if the weather is favourable) we 

 shall perhaps find this method of finding the lon- 

 gitude of places as accurate as most others ; at least 

 it is the most easy, and attended with the least ex- 

 pense to the observer. Every ship that goes to 

 foreign parts is, or may be, supplied with a sufficient 

 number of quadrants at a small expense ; I mean 

 good ones, proper for making these observations. 

 For the difference of the price between a good and 

 bad one, I apprehend, can never be an object with 

 an officer. The most expensive article, and what is 

 in some measure necessary in order to arrive at the 

 utmost accuracy, is a good watch ; but for common 

 use, and where that strict accuracy is not required, 

 this may be dispensed with. I have observed before, 

 in this journal, that this method of finding the lon- 

 gitude is not so difficult but that any man, with 

 proper application, and a little practice, may soon 

 learn to make these observations as well as the 

 astronomers themselves. I have seldom known any 

 material difference between the observations made 

 by Mr. Wales, and those made by the officers at the 

 same time. * 



In observing the variation of the magnetic needle, 

 we found, as usual, our compasses differ among them- 

 selves, sometimes near c 2° ; the same compass, too, 

 would sometimes make nearly this difference in the 

 variation on different days, and even between the 

 morning and evening of the same day, when our 

 change of situation has been but very little. By 



* See Vol. III. 



