The Philosophical magazine; a journal of theoretical, experimental and applied physics . laced con-tiguous to the object; the stop-cock is to be opened so as to allowa free supply of gas to the burner, which is now to be kindled; theheat now begins to act on the air contained in the ball of the in-strument, causing it to expand and force the mercury up the stemA; when it is found, by the use of a conmion liiermometer, that theheat has risen to 100°, the tube C is to be pushed down till itslower extremity is immersed in the mercury. This would, of course,cause the flame to be extinguished ; but
The Philosophical magazine; a journal of theoretical, experimental and applied physics . laced con-tiguous to the object; the stop-cock is to be opened so as to allowa free supply of gas to the burner, which is now to be kindled; theheat now begins to act on the air contained in the ball of the in-strument, causing it to expand and force the mercury up the stemA; when it is found, by the use of a conmion liiermometer, that theheat has risen to 100°, the tube C is to be pushed down till itslower extremity is immersed in the mercury. This would, of course,cause the flame to be extinguished ; but, to prevent this occurring,a small hole is bored through the inner tube opposite F, which per-mits a small quantity of gas to pass to the burner. As the passageof the gas is now interrupted, the source of heat is withdrawn, andthe cooling influence of the surrounding air comes into play, whichwill cause the air contained in B to contract and the mercury tosink in A, leaving the end of C uncovered, and thus open a freepassage to the gas, which by its combustion would again raise the. Intelligence and Miscellaneous Articles. 485 temperature so as to cut off the supply; but in a very short timethese two opposing forces come to an equilibriuu), and the Hamescarcelj varies in size. After trying the instrument in the form described, I experienceda practical difficulty from the want of perfect contact between theend of the tube C and the mercury, from which I found that itmight rise many degrees beyond the assigned limit without sufficientlylowering tlie flame; this I at once saw might be overcome by makingthe tube of a substance which would become wetted by the tried a brass and also a copper tube, amalgamated at the end, butthey slowly dissolved in the mercury, which they rendered impure,so that its rise and fall could not be depended on with the retpiirtdnicety. The substance now used is platinum, of which about halfan inch of the lower end of the tube is formed, amalga
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