140 C. Barus — Criticism of Mr. Fish 



er's 



Art. XXI. — Criticism of Mr. Fisher's Remarks on Bock 

 Fusion; by Carl Barus. 



Although the experiments of Profs. Roberts-Austen and 

 Riicker* were made in answer to a query of Mr. Fisher's, I 

 think he is laboring under a misapprehension as to their work. 

 These gentlemen nowhere state that the rock was fused below 

 920°. What they do state is, " There is a large absorption of 

 heat in the neighborhood of 800°, which raises the mean 

 specific heat between 750° and 880° C, to the large value 

 0*636 ;" and in an earlier paragraph, " frequent heatings and 

 coolings, and the nature of the flame — whether oxydizing or 

 reducing — employed to heat the mass appeared to affect the 

 results very seriously." 



As the paper of Roberts- Austen and Riicker appeared about 

 the time when I was making the diabase experiments, I 

 looked forward to these anomalies (as I believed them to be) 

 with interest — more particularly as Mr. King and I were on 

 the lookout for polymerizations accompanied as they usually 

 are with marked volume changes. But my results showed 

 such commonplace smoothness throughout the stated interval 

 of temperature that I gave up the chase. If, however, these 

 anomalies are now to be interpreted as fusion, it is well to 

 bear in mind that the melting point of silver is at about 954° ; 

 and that if dolerite melts even below 920° (750° to 880° as 

 given above) it ought actually to run on a surface of boiling 

 zinc. 



We did not try dolerite. True we had a list of rocks to 

 put through the mill after it had been invented ; — but Con- 

 gress in its wisdom saw no public value in our lucubrations 

 and our efforts (with much else on our program) were fore- 

 doomed. It is with mingled feelings that one apologizes for 

 one's toddling paces when there was good will enough for a 

 journey ! 



However, to believe that dolerite can be slagged in a zinc 

 pot or even fused in a candle flame is an exertion, and one is 

 at liberty to ask the privilege of trying it. 



Suppose for the sake of argument, that an absolute tempera- 

 ture 920°+273° is inserted into Clausen's equation instead of 

 1170°+273°. The effect would be to change the accepted 

 relation of the increments melting point and pressure from 



* Roberts- Austen and Riicker, Phil. Mag., xxxii, p. 353, 1891. With regard 

 to these experiments I have already expressed myself in Phil. Mag , xxxv, pp. 

 296, 305, 1893. The authors themselves state " As we have not definitely proved 

 what is the cause of these discrepancies " (those of the above text being meant), 

 "we publish our conclusions with a certain amount of reserve." 



