HOLMAN, LAWRENCE, BARR. MELTING POINTS. 229 



Inspection of columns six and seven, Table I., will show that the 

 computed boiling points of water and napthalin by the exponential and 

 logarithmic equations depart widely from the known temperatures in 

 opposite directions, by about equal amounts, and in the directions 

 according with the departures from the Barus and Holborn and Wien 

 data. Also, that the difFereuces between the computed melting points 

 intermediate between sulphur and gold differ but slightly by the two 

 formulae, thus confirming the former conclusions. It is obvious, thei'e- 

 fore, that although either of the two formulae would yield fairly good 

 interpolations for Al, Ag, and Cu, yet that a mean between the two 

 would probably quite nearly offset against each other the systematic 

 errors of the respective equations. This is also true in the dangerous 

 process of extrapolation for the platinum melting point, where the 

 chances of error in the result seem to be probably very much reduced 

 by averaging. The means of the melting points computed by the 

 exponential and logarithmic equations are, therefore, regarded as the 

 nearest available approximations, and the round numbers of column 

 nine are adopted as provisional values to represent the results of 

 the work. 



Comparison of the results of the Avenarius formula, column five, 

 will show that they depart widely from the others in the direction 

 which would have been anticipated from the conclusions of the pre- 

 vious paper, thus further strengthening those inferences. 



In addition to the foregoing, the melting points of three other 

 samples of copper, and one other of gold, were measured. The gold 

 was dentists' gold " foil," purchased in Boston. This is usually 

 classed as " very nearly pure," but its analysis was not known. No 

 special interest, therefore, attaches to it beyond the indication that it 

 gives of the sign and order of magnitude of the error (about — 4°) 

 which would be introduced by the use of such gold in the calibration 

 of the Le Chatelier pyrometer, or in similar ways.* The melting 

 point was found to be 10G8°. 



The four coppers yielded the appended results. 



* Hohnan, Calibration of the Le Chatelier Thermo-electric Pyrometer. 

 See These Proceedings, j^ost, p. 234. 



