632 



THE POPULAR SCIENCE MONTHLY. 



nary flat films ; the outlines are sometimes very singular, being 

 made up of most eccentric curves in all sorts of combination. In 

 one or two instances these scales overlapped, showing that the 

 disintegration had taken place in a spiral direction (Fig. 10, B). 

 This world of beauty, in both colors and form, was found within 

 the area of one square inch or less, on a small fragment of 

 no special brilliancy to the naked eye. 



Brewster describes, in the " Transactions of the Edinburgh 



Royal Society," some specimens 

 A of ancient decomposed glass, 



but they must have been in a 

 much earlier stage of decom- 

 position than the Cesnola glass, 

 judging from the figures and 

 Jf descriptions given. He states 



^ 



Pig. 10. Cesnola Glass. 



A. a, emerald-green, with strings of bubbles light-green and brilliant, like pale emeralds ; 6, 

 bronze-gold ground, spots of violet, and bronze-gold rings, ruby, pale vivid blue, and deep 

 sapphire blue ; c, partly scaled film, vivid violet, toning down, with spots as above; d, deep 

 violet-blue, like the sky on certain nights ; e, speckled gold ; /, exquisite violet, with bubbles 

 Jike pearls, only shaded violet tone. 



B. Shape of violet layer as it came off, very thin. 



that the experiment had been made of submitting glass to power- 

 ful solvents, when, in a short time, circles and other forms, centers 

 of decomposition, began to appear. Here was probably the sug- 

 gestion which has since been followed in the manufacture of our 

 modern iridescent glass. In a piece of iridescent glass, brilliant 

 at first, but which has been growing more brilliant for several 

 years, I find a number of distinct centers of disintegration, show- 

 ing the process, whether by art or by time, to be identical in kind. 



The question involved in the problem of air navigation is regarded by Mr. E. 

 N. Lewis as simply one of increasing power without increasing the weight of the 

 apparatus by which the power is applied. The supposition that the vehicle must 

 be lighter than the air, on which experiment has mostly proceeded, is a mistaken 

 one. " A bird can fly, not because it is comparatively light in weight (for it is 

 not), but because it is strong." The successful air-ship will be a large structure, 

 very light in weight compared with its strength, but many times heavier than the 

 air it displaces, and propelled by machinery capable of developing enormous power. 

 " The skill which has produced . . . the modern bicycle will not find the task of 

 designing such a structure too difficult." 



