Waters in the Estuaries of the Mersey and Clyde, 111 



rent, produced a slight motion among the particles, it was 

 seen distinctly ; it was also very apparent when the surface 

 of the water was struck with the hand. When the hot air 

 from a chimney mixes with the colder atmosphere, or when 

 two transparent fluidsjof different densities are mingled to- 

 gether, the same change is seen ; and there could be no doubt 

 whatever, that at the time in question, there were two films 

 of water, of different densities, which were mixed when the 

 surface was broken. What occasioned these two strata of 

 water I am not prepared to speak of ; but should further ob- 

 servations in other localities where the water is clear and 

 occasionally very smooth, shew that this is a general, and 

 not a rare or partial state of the surface of sea water, it ap- 

 pears to me to be extremely probable, that luminous crested 

 waves by night accompany like conditions. 



About the time I was engaged with these observations, I 

 met with an amusing instance of the belief, among sea-faring 

 men, of the power of the moon's rays to dispel thin fogs. I 

 had remarked to the look-out man on the gangway of a 

 steamboat, that I supposed the thin fog then resting on the 

 surface of the sea had been troubling them for the last eight 

 or ten days \ He answered it had. Then, I suppose by night 

 it troubles you the most \ " Yes, Sir, but the moon has all 

 the time been shining very strong, and she scratches it up 

 pretty well." This belief in the influence of the lunar rays 

 over thin vapours, is quite in accordance with what I have 

 often heard of from sailors ; and now that M. Melloni has 

 clearly established the fact of a calorific power in the rays 

 from the moon, it becomes interesting to inquire, whether or 

 not this popular observation has correctly anticipated the 

 careful researches of men of science. 



