459 three, but by a series, of observations" it cannot be too strong~lurged that this work should m each case accompany the record of results, when expressed in platinum-temperatures ; and no one will deny that to have these results expressed at once in terms of the normal air-thermometer will permanently enhance the value of the work in such a manner as to mnply recompense the extra labour. With the view of helping towards this desirable end I have endeavoured to show that the simple formula

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... ) is superior to th~ joint formuke (3) and (4) . Peterhouse, Cambridge, August 1897. LIX. 0~ Real and Apparent Freezing-Points and the Freezing-Point Methods.