90 OUR HERITAGE THE SEA 



The mares' tails being the wispy curling wreaths of 

 cirrus cloud, and the mackerel backs the fluffy little 

 combinations of cirrus and cumulus cloud that are 

 known to the weather-wise as the cirro-cumulus. 

 Few of the celestial pictures presented by the clouds 

 are more beautiful than that often presented on a 

 fine summer's day by the mackerel-back clouds lying 

 in their long rows of fleecy tufts against the delicate 

 azure of the sky, and giving it a curious dappling of 

 white and blue, which is exceedingly charming in its 

 prettiness. And when this arrangement of the higher 

 cloud-forms obtains at sunrise or sunset, and catches 

 the sheen of the sun's rays, the effect is gorgeous 

 beyond all power of words to describe with any ap- 

 proach to adequacy. 



But beautiful and picturesque as are these higher 

 cloud-forms, it is difficult indeed to say what useful 

 purpose they subserve, or how they minister to the 

 great combined work of the atmospheric and oceanic 

 phenomena. Floating high above the turmoil of the 

 lower air strata, they appear to the imaginative mind 

 as dwelling apart in serene aloofness, having no part 

 or lot in mundane matters. Of course, as they are 

 a part of our atmospheric system, they must perform 

 their allotted task in their appointed way ; but what 

 that task is, or how it is performed, is far beyond our 

 ken. The work of the cumuli is comparatively easy to 

 understand, as well as their decorative value, although 

 one part of that work the gathering and storing of 

 electricity is sufficiently mysterious to puzzle the 

 deepest thinkers of the world, who, indeed, have not 

 yet been able to say what electricity is. Most likely 

 the work of the cirrus is just as important, but until 



