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[ 84 The (rnall bowl at the top, with beads therein, render it far kis liable to break by the mencury's afeent, the bowl giving it an immediate expanic from the colon, and the beads counteratting its force as fo many fprings, which has filch an circa, that from many experiments (purpofely made) I have found it no eafy matter to break it by the memory's afcent, which is very city in the common one ; yea, it even ftequently breaks, if the greateft caution is convenience.

not taken in turning it. Its fo won vaunted by boiling the quickfilver in the tube, that I depend on its being luminous after being carried fo far ; and, as a

further proof. I doubt not of your finding the elevation above any other. The tube may be as large as you pleafe ; but, if fo, it lhould not be continued further than the tubes curve, which fhould have its colon fmall (no inconvenince to the inflrument, which may othcrwife take air) by the tube's bring drawn fo,

or, what is better, one of the fmallea bore being joined themto. This barometer may be conveniently carried, in.

vetted, in a walking-flick, with a Male contained in. a large tube covering the other, which I lbould have completed, had I had a fit tube. The beads, at a certain time, may be apt to detain a little mercury in the bowl; but that is to be eafily re-

united by flaking it, or muting it to tr-afcend therein. The infirtunent might bane been fomewhat neater, had I (inftead of turning it.at the lanip with a blow-pipe) rendered the tube flexible over a charcoal

tire, and turned it on a flick of pipe-maker's clay, but I could not procure it. Cauflon

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