1 
1 8 Mr. Sms’ a ton’s Obfervaticns on the :/ 
purpofe of afcertaining the longitude at fea (which inftruments 
for this purpofe- required a degree of accuracy and certainty in the 
divifion, by no means neceffary thereto when applied to the fimple 
purpofe of obferving latitudes) ; 1 fay, for thefe eonfiderations, Mr. 
Ramsden determined to let about fometh in g in the inftru mental 
way, that Chou I'd be fufficient effectually to anfwer thefe purpofes. 
Accordingly, confidering.the nature of the endlefs fcrew, . he 
fet him fell to work upon an engine whofe divided wheel or plate 
was of thirty inches diameter; and though the performance of 
^h is firft eflay was- inferior to his expectations and wifhes, yefr 
with it he was able to divide theodolites with a degree of preci- 
onh far ftsperior to any tiiingof the kind that had been exhibited 
fito te; public. 
This engine I myfelf faw in the fpring of the year I 768' ; and 
it appeared to me not only a very laudable attempt towards in- 
ftrumental divifion s, but a very good model for the con ft ruction 
of an engine of the mold accurate kind for that purpofe.. And. 
he furthermore, at the fame time, ffiewed me. the model or 
pattern for catling a wheel of a much larger fize, which he pro- 
pofed to make' upon the fame plan, and with confiderable im- 
provements. This being effected fome time in or about the year 
Fp74, its accuracy was proved 4 by making a fextant, afterwards* 
fubjected to the examination of Mr. Bird; who in confiequence 
approved the method, not only as- fully fufficient for the divi- 
fon of Hadley’s fextants and octants for any purpofe whatfo^ 
ever, but in faCt for dividing any inftrument whofe radius did 
not exceed that of the dividing wheel* which was. forty -five; 
inches in diameter : whereupon the Board of Longitude, ever 
ready to encourage all endeavours that tend to the certainty and 
perfection of any thing fubfervient to the purpofe of finding the 
longitude at fea, very properly and ufefully refolved to confec 
aifc 
