Saint Bartholomew's Hospital reports . o of the absolute temperatures of thebody and of the surface to which it cools. The problem may be thus expressed:— Let S = area of the body surface in square = thermal emissivity of the surface. Then ^aS = heat lost per second from the whole surface if thesurface is i° hotter than the surroundino: medium. Let 6 =: excess of in an infinitely short time, denoted by dx, heat lost = USddxDenote by Jf and G the mass and specific heat of the body, andby — dO the infinitely small fall in temperature of the surfaceaccompanying the
Saint Bartholomew's Hospital reports . o of the absolute temperatures of thebody and of the surface to which it cools. The problem may be thus expressed:— Let S = area of the body surface in square = thermal emissivity of the surface. Then ^aS = heat lost per second from the whole surface if thesurface is i° hotter than the surroundino: medium. Let 6 =: excess of in an infinitely short time, denoted by dx, heat lost = USddxDenote by Jf and G the mass and specific heat of the body, andby — dO the infinitely small fall in temperature of the surfaceaccompanying the infinitely suiaR loss of heat. Then we have— - dOMO = usedx-de _ES ?, In any experimental case it would be an almost impossible pro-blem to determine separately the values of E, 0, M, and aS^, varying 2 54 Proceedings of the Aheniethian Society. so largely as they do from one body to another, but we may write __ = k a. quantity which is readily determinable for any one MC body ; hence we should have on integration— k 1 dx M. — log^ 6 = kxIn other words, if a curve is drawn the ordinates of which, Aa,Bh, denote excesses of temperature, and the abscissoe, ab, 5c, denote times, the lengths of successiveordinates equally distant apartwill represent the successive termsof a diminishing geometrical pro-gression. Hence, assuming forthe moment the simple case of anunchanging temperature of ex-ternal medium, it will be possibleto construct the curve represent-ing the post-mortem fall of tem-perature, and hence to calculatehow long it is since the momentof death corresponding to a known excess of temperature of thebody surface. Or if two careful observations of temperature aremade at a few minutes apart, it is possible by means of a mathe-matical formula or by a geometrical construction to determinewithin a small error the moment at which the person died, pro-vided only that the body has not yet reached the temperature ofthe surrounding medium. The cases in which the investiga
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Keywords: ., bookcentury1800, bookdecade1860, bookpublisherlondo, bookyear1865
