514 



SCIENCE 



[Vol. LV, No. 1428 



DISCUSSION AND CORRESPOND- 

 ENCE 

 DID HUMPHRY DAVY MELT ICE BY 

 RUBBING TWO PIECES TOGETHER 

 UNDER THE RECEIVER OF 

 AN AIR PUMP ? 



It is eommonly stated that Humphry Davy 

 melted two pieces of ice by rubbing them to- 

 gether under the exhausted receiver of an air 

 pump, and thus showed conclusively that heat 

 is not a material substance. In books which 

 I happen to have at hand I find twelve different 

 authors stating that Davy melted two pieces 

 of ice by rubbing them together in a vacuimi, 

 and four of them stating in addition that the 

 two pieces of ice were rubbed together by 

 clockwork. In looking to see what Davy him- 

 self said about this experiment I have, to my 

 surprise, failed to find any evidence that he 

 ever performed just this experiment. 



Of the authoi-s whom I consulted, four give 

 references. Two refer to the Collected Works 

 of Sir Humphry Davy, vol. 2, p. 11. The 

 other two refer to Davy's Elements of Chem- 

 ical Philosophy. In the Elements of Chem- 

 ical Philosophy, reprinted as Volnme 4 of the 

 Collected Works, I have not found any state- 

 ment about the melting of ice by friction. In 

 the first paper ia Volume 2 of the Collected 

 Works Davy describes twenty-two experiments 

 and makes comments on them. 



In Experiment 2, p. 11, he describes an ex- 

 periment in which "by a peculiar mechanism" 

 he caused two blocks of ice to rub together. 

 "They were almost entirely converted into 

 water." In the description of this experiment 

 nothing is said about any air pump. 



The description of the third experiment is 

 not entirely clear. Davy says, "I procured a 

 piece of clock-work so constructed as to be 

 set to work in the exhausted receiver; one of 

 the external wheels of this machine came in 

 contact with a thin metallic plate. A con- 

 siderable degree of sensible heat was produced 

 by friction between the wheel and plate when 

 the machine worked uninsulated from bodies 

 capable of communicating heat. I next pro- 



cured a small piece of ice; round the superior 

 edge of this a small canal was made and filled 

 with water. The machine was placed on the 

 ice, but not in contact with the water. Thus 

 disposed, the whole was placed under the re- 

 ceiver The receiver was now ex- 

 hausted The machine was now set 



to work. The wax rapidly melting, proved 

 the increase of temperature." 



From this description it seems that the clock- 

 work was not a mechanism for rubbing two 

 pieces of ice together, but was used to pro- 

 duce friction between two metals, and that 

 the heat developed by this friction caused the 

 melting of some wax. 



Any clockwork which Davy might have 

 placed inside of the receiver would probably 

 not have been sufficiently powerful to melt 

 ice rapidly by rubbing it on ice. I have 

 wondered if some author did not read the sec- 

 ond experiment, glance at the third, and see- 

 ing the words clockwork, exhausted receiver, 

 ice conclude that two blocks of ice were rubbed 

 together by clockwork under the exhausted re- 

 ceiver. If so, this is an interesting illustra- 

 tion of the ease with which a misstatement may 

 pass from one author to another. If there is 

 evidence that Davy did melt two blocks of 

 ice by causing clockwork to rub them together 

 under the receiver of an air pump I hope some 

 one will adduce it. 



Arthue Taber Jones 

 Smith College, 

 Febbuaky 23, 1922 



A PARACELSUS LIBRARY IN THIS COUNTRY 



In your issue of February 10, F. N. Gar- 

 rison announces a new prospective publication 

 in Germany of the complete works of Para- 

 celsus, that great pioneer in analytical chem- 

 istry and medical reformer of the sixteenth 

 century. It may not be generally known that 

 what is no doubt the largest and most complete 

 collection of the works of Paracelsus in this 

 country is the one made during the last century 

 by the late Dr. Constantine Hering of Phila- 

 delphia, and since his death in 1880 was ac- 



