92 Mr. C. Tomlinson on some Phenomena 



condensed in the two bulbs. M. Donny remarks that this ex- 

 periment is of a nature to show that the forces of cohesion and 

 adhesion may play a very important part in the ebullition of 

 water, the cohesion of water being thus supposed to be superior to a 

 pressure of three atmospheres, or a column of water of 30 metres. 



These are important conclusions, and ought not, as it seems 

 to me, to rest on such data as the above experiment affords ; for 

 I cannot help thinking that it is a false inference to conclude 

 that because the tube containing the water was kept in the hot 

 baths during eleven and a half minutes, the water necessarily 

 acquired the temperature of the baths. No evidence short of 

 the actual reading of a thermometer in the water, as well as in 

 the hot baths, ought to warrant so marvellous a statement as that 

 water not under pressure (not even atmospheric in Donny's ex- 

 periment) can be heated to 280° F. without boiling. 



In like manner, it seems to me that M. Gernez has been led 

 into error by his mode of operating. He had a thermometer in 

 his hot bath (water or paraffine) with the bulb near to the tube 

 containing the liquid ; and assuming that the liquid in the tube 

 must be of the temperature of the bath, he states that such 

 liquids as chloroform, wood-spirit, and bisulphide of carbon can 

 support a temperature of 100° C. (2 J 2° F.) without boiling; 

 that is, that bisulphide of carbon can be raised 9i° F., chloro- 

 form 70°, and wood-spirit 64° above their boiling-points without 

 boiling, even when not under pressure. 



Now, among the numerous experiments that I have tried with 

 wood-spirit and other liquids in the only way that seems to me 

 to lead to satisfactory results, namely with a thermometer in 

 the liquid as well as in the hot bath, I have never seen the 

 liquid rise to any thing like the temperature of the bath; and 

 how is it possible that it can do so, seeing that distillation is 

 constantly going on from the surface of the liquid ; and although 

 it may rise many degrees above its boiling-point, yet the tension 

 of the pent-up vapour at length asserts itself long before the 

 liquid has acquired the temperature of the bath. Even in 

 Donny's experiment with a tube not more than T a inch in dia- 

 meter, the preliminary operation of boiling the water shows that 

 evaporation from the surface must have been going on in the 

 hot baths ; and this of itself was sufficient to keep down the 

 temperature. 



I requested my friend and former colleague, Mr, "W. H. 

 Hatcher, to conduct for me in his laboratory a series of expe- 

 riments on the superheating of liquids, such as I could not 

 readily carry on in a private house; and I have to thank him 

 and his assistant, Mr. C. Rumble, for the care and skill with 

 which they have carried out my wishes. 



