Page:Voyage in search of La Perouse, volume 1 (Stockdale).djvu/101

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of la perouse.

being much ſtronger than thoſe of copper, do not yield to that degree of preHure which bends the others. This fource of error affords an additional tea- fon why mariners ought to give the preference to the circle of reflexion, invented by Citizen Borda. The facility with which any errors that may arifc from the graduation, are redified by crois obfe'rva- tionSj in the ufe of this inftrument^ gives it a very great fuperiority over all others. I regret that this valuable inilrument, though. {o eaiy in its application, is not more generally in ufe. Each of our ofiicers poiTelTed one of them, and during the courfe of the expedition every one learnt to ufe it with certainty. With a little pra6lice an obferver may take the longitude within 10, or 15,000 toifes; and there is reafon to believe, that when the lunar tables fliall ftave attained a greater degree of perfed;ion, the obfervations will approximate ftill nearer to the truth. Though the plants which I had colle<fled at Teneriffe were very dry when we failed from that liland, they were becom.e much damaged by the moifture which they had imbibed, during tho. time that we were between the Tropics, particu- larly at the lower part of the leaves, where the abforbent