288 POPULAR HISTORY OF THE AQUARIUM. 



written much, although it is known that many of these 

 animals possess the power of illuminating the ocean, and 

 some of them may be induced to exhibit their peculiarity in 

 confinement. The Tyrosomay for instance, has been de- 

 scribed as presenting a very luminous appearance seen in 

 a tank by night. AYhen in motion it changes, passing 

 through the colours of a bar of red-hot iron to that of a 

 white heat, represented by a phosphorescent colour. We 

 have seen the heads of common Mackerel shining brightly 

 in a dark cellar ; and, as Mr. Swainson has observed, 

 ''When we consider how many hundreds of species, more 

 especially those which live in deep water, are covered with 

 scales of a rich and shining silver hue, infinitely more bril- 

 liant when those fishes are alive and in their native element 

 than as they are commonly seen after having been caught, 

 it becomes highly probable that the brilHant radiance with 

 which they are clothed, is to effect some other purpose than 

 mere ornament." Although Herrings have not yet been 

 kept in Aquaria, it will not be uninteresting to conclude 

 this Chapter with the following account of their brilliant 

 luminosity, by Hugh Miller, in ' My Schools and School- 

 masters.^ 



"As the night gradually darkened, the sky assumed a 



