204 IMPROVEMENT IN TIME-PIECES. 



made than by with very little trouble ; and, fecondly, the longitude can be 



other methods, found oftener by a time-keeper than by any other means. I 



have not met with a more ftriking proof of this pofition, than 



in the voyage of La Peroufe round the world in the (hip La 



Remarkable cafe Bouflble. Between the 1ft of Auguft 1785, and the 8th of 



in proof. September 1787, this celebrated navigator took only 72 lunar 



obfervations ; but he took 393 obfervations on the longitude 



by his time-keeper No. 19. This is an unequivocal proof of 



the benefits that navigation derives from this mode of finding 



the longitude. 



But time- keep- It is to be regretted, however, that time-keepers are ex- 



ers are very ex- pgnftve and liable to ftop, or go irregularly. Were it not for 



liable to irregu- thefe inconveniences, no other method of finding the longi- 



^'^^y* tude need be fought after. But a difcovery was made by Mr. 



1 Barraud, about the clofe of the laft century, on the effeds of 



oil on time-keepers, which not only reduces them in price, 



but contributes to their performing with greater precifion. 



Difcovery of Mr. Barraud had frequently communicated to me his im- 



Mr. ^5^"^^*^^ provements in chronometry, but this difcovery on the effeds 



keepers areren- of oil, appeared a matter of fo much importance, that I wrote 



dered more per- ^^ ^^-^^ requefting his leave to publifli it, and the following 



cheaper. extract is taken from his obliging anlwer. 



To Mr. WALKER. 



DEAR SIR, London, Jan, 2^ i 1804-. 



Letter from Mr. I AM much pleafed to find that it is your intention to favour 



Banaud. \]^q public with your obfervations on chronometry, and fliall 



derive fatisfadion in contributing my mite to fo defirable an 



end : you are therefore welcome to ufe fuch information as my 



experience of fads enables me to furnifli. 



Jewelling the The ftate of my regulator I have already defcribed [in a 



holes of time- f^^mer letter! , from which I infer, that fo far from jewelled 

 keepers IS inju- -• . , , , r i i 



riousj holes being advantageous in clock-work, they are ablolutely 



injurious. That they are equally fo in chronometers, I have 



had abundant experience, having found, almoft without ex- 



the oil in fuch ception, in chronometers coming oft' a long voyage, the oil in 



holes bt'ng ^ much worfe condition in the jewelled holes (particularly in 



than in brafs thofe where the fridion was confiderable) than in the brafs 



holes. ones. I have therefore been induced, in every inftance, to 



rejed jewelled holes, and introduce thofe of brafs, and the 



altcralirii 



