204 Dr. E. J. Mills. [Dec. 22, 



temperature at which certain organic substances pass from the solid 

 to the liquid state. 



The apparatus, of which an engraving, on a scale of one-fourth,* is 

 given below, consists of a bath nearly filled with oil of vitriol. In this is 



inserted a glass funnel, having on its lower edge six equidistant semi- 

 circular cuts of about 5 millims. radius, and, at the end of the neck, four 

 of the same. A thin test-tube, resting freely on the funnel, contains 

 a bath of paraffin oil, in which the thermometer's bulb is centrally 

 placed; against the bulb, in a little tube separately represented, is 

 fixed the substance whose melting point is to be determined. When 

 the large bath is heated, constrained and regular convection takes place 

 in the liquid ; the effect upon the thermometer is such as to cause the 

 mercury to rise with very great steadiness. 



A preliminary series of researches in thermometry has enabled me 

 to give a series of results completely corrected, and in terms of the 

 air thermometer. 



* The portion above the cover of the bath is not to scale. 



