364 J7. Melloni on Dew. 



premonition of what was to produce a remarkable destruc- 

 tion among fish, was the discoloration of the water of the 

 bay, from a marine green to a dirty milk-white hue, followed 

 by a decided odour of the gas ; so much of it being present 

 on many occasions as directly to blacken a clean piece of 

 silver, and to blacken paint- work in a few hours. 



The fish, during this evolution, rose in vast numbers from 

 the bottom, and after struggling for some time in convul- 

 sions upon the surface, died. 



I was particularly struck by this fact, that all of them, 

 during the time they were under its influence, acted in pre- 

 cisely the same manner. The first thing noticeable with 

 regard to its effect upon them was, that on coming near the 

 surface, they seemed to have much difficulty in remaining 

 below it at all. They then rose completely to the surface, 

 struggling vainly to dive beneath. This was followed by a 

 violent springing and darting in various directions, — evident- 

 ly without control of direction — for they moved sideways, or 

 upon the back, and sometimes tail first, with great velocity. 

 After a little time their motion became circular, and upon 

 the back, the circle of gyration constantly diminishing, and 

 the rapidity of the motion as constantly increasing, until 

 there was a sudden cessation of all motion. The head then 

 floated above the surface, the body being in a perpendicular 

 position. A few convulsive movements shortly followed, and 

 they were dead. 



I have watched thousands of them so dying, and in every 

 instance such was the mode of death. Having taken them 

 at the moment of death, and immediately after, a rude exa- 

 mination shewed in all the same appearance. The intestines 

 and brain were gorged with blood, much darker than natural. 

 The gills were almost black, and the air-bladder ruptured. 



, 



M. Melloni on Dew. 



Dew is not an immediate effect of the cooling produced by 

 the nocturnal radiation of vegetables on the vapour of the 

 atmosphere, as most treatises on physics and meteorology 



