114 Prof. T. G. Bonney. On the [June 19, 



In "Watson's Chemical Essays" (vol. i, 5th Edn., 1789, p. 73, 

 note) the experiment is again described in the following terms: 



" It is a very remarkable phenomenon that a vessel containing 

 water will never boil, how long soever it be exposed to the action of 

 boiling water. A common bottle is filled with water, and placed in a 

 pan of water so that the mouth of the bottle be a little above the 

 water in the pan. The pan is set on the fire, and its contents made 

 to boil violently at 212 F., while the water in the bottle will only 

 reach 202." 



In repeating this experiment, I used for the outer vessel a large 

 wide-mouthed flask filled about two-thirds with water, heated by 

 means of a spirit lamp ; and for the inner vessel a glass tube, 

 suspended by means of a string attached to the top ring of the retort 

 stand which supported the flask. In this way the tube could be 

 raised or lowered so as to place the level of the water contained in it 

 above or below the level of the water in the flask. 



The experiment, under this form, has been frequently repeated, and 

 it was found that, in general, after the water in the flask had been 

 boiling for some time, the temperature of the water in the tube was 

 not more than 1 or 2 F. below that in the outer vessel. 



The inferior temperature of the water in the tube is evidently due 

 to evaporation ; and as there were no very clear ideas on this subject 

 until the time of Dal ton, the early observers regarded the result as 

 paradoxical. 



On covering the water in the tube with a layer of oil, the tempera- 

 ture rose to that of the water in the flask, and bubbles of steam 

 escaped freely from the surface of the water through the oil. 



The oil used was olive in one case, and a volatile oil of high 

 boiling point, such as cajuput, in another. On passing the thermo- 

 meter through the oil down into the tube, bubbles of steam were 

 given off freely from the bulb and stem, thus further illusti-ating one 

 of the points maintained in my paper on the action of nuclei in 

 liberating vapour from boiling liquids, contained in the "Proceedings 

 of the Royal Society," vol. 17, p. 240. 



VI. " Notes on the Microscopic Structure of some Rocks from 

 the Andes of Ecuador, collected by E. Whymper. No. III. 

 Cotopaxi and Chimborazo." By Professor T. G. BOXXEY, 

 D.Sc., F.R.S. Received June 6, 1884. 



In regard to these two important volcanic mountains of the 

 Ecuadorian Andes, Mr. Whymper has favoured me with some de- 

 scriptive noieu, which appear to me of so much interest that I incor- 

 porate them with but slight modification into my paper. 



