and the Mode of its Communication. 101 



by metals so much more strongly than water that even 

 the weight of a drop of water is not sufficient to force 

 away the stratum of air which covers and adheres to the 

 surface of a metal on which the drop reposes; but at 

 lower temperatures this does not seem to be the case. 



The following experiment, which I made several 

 months ago with a view to investigate the cause of the 

 slow evaporation of drops of water placed on hot metals, 

 will, I think, throw much light on this subject. 



Experiment No. 34. Taking a clean polished silver 

 spoon, I blackened the inside of it by holding it over 

 the flame of a wax candle ; then, putting a large drop of 

 water into it, I found, as I expected, that the drop took 

 a spherical form, and rolled about in the spoon without 

 wetting its blackened surface. 



I now held the spoon over the flame of a candle, and 

 attempted to make the water boil ; but I found it to be 

 absolutely impossible. The handle of the spoon became 

 so very hot that I could not hold it in my hand without 

 being burnt, though it was wrapped up in three or four 

 thicknesses of linen ; but still the drop of water did not 

 appear to be at all affected by this intense heat. If the 

 bowl of the spoon were touched with the finger, a hissing 

 noise announced that it was extremely hot ; but still the 

 water remained perfectly quiet in the spoon without be- 

 ing evaporated. 



Having in vain attempted to make this drop of water 

 boil, and not being able to hold the spoon over the 

 flame of the candle any longer on account of the heat of 

 its handle, I now poured the drop into the palm of my 

 hand. I found it to be warm, but by no means scald- 

 ing hot. 



By holding the spoon with a pair of tongs over the 



