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THE POPULAR SCIENCE MONTHLY. 



The phosphorescent power of barium sul- 

 phide was discovered in 1675. Canton, in 

 1761, discovered the so-called phosphorus 

 which bears his name by calcining oyster- 

 shells with sulphur so as to form the cal- 

 cium sulphide, the most remarkable of phos- 

 phorescent substances. Its luminosity ap- 

 pears to be permanent, for Professor Hea- 

 ton, in a lecture describing the qualities of 

 the luminous paint, delivered before the 

 Society of Arts, on the 11th of March last, 

 exhibited a specimen of it which had been 

 sealed in glass by Canton himself in 1764, 

 and which still glowed. The power is at- 

 tributed to a property which the substances 

 possessing it have of absorbing rays and 

 afterward emitting them with an increased 

 wave-length, as is remarkably shown by qui- 

 nine, which shines after having been ex- 

 posed to the ultra-violet part of the spec- 

 trum, and converts invisible actinic into 

 visible light-rays. The late Mr. Balmain 

 succeeded in producing from a compound 

 of lime and sulphur a constant and very 

 powerful phosphorescent substance, which 

 he patented and applied as a paint ; ar- 

 ticles coated with it become luminous after 

 exposure to the light and retain their glow 

 for a considerable length of time. The 

 sensitiveness of this substance was shown 

 during Professor Heaton's lecture by pass- 

 ing electric sparks in front of a card painted 

 with it which had been previously kept in 

 darkness. Each spark impressed its image 

 on the card, and made it luminous. Even 

 a lucifer-match struck in front of a dark 

 pane produced a visible effect on the paint. 

 The highest effect is produced by the violet 

 and ultra-violet rays. The red and yellow 

 rays do not add to the luminosity ; in fact, 

 they diminish it when they are allowed to 

 continue to act for a considerable time. 

 This is owing to their calorific effect, which, 

 though it may stimulate the light for a 

 while, in the end causes it to disappear more 

 rapidly. A short exposure of the paint to 

 ordinary daylight is sufficient to produce a 

 high degree of illumination, the amount and 

 duration of which will depend considerably 

 on the quantity and quality of the light and 

 on other conditions. " When the paint has 

 been exposed to the intense light of the sun 

 or of burning magnesium, a good deal of the 

 brilliancy disappears quickly, but after that 



\ the fading is very slow ; and it may be said 

 that a more or less useful light will remain 

 through the length of an ordinary winter's 

 night. In one case, Professor Heaton was 

 just able to see the dial of a watch by the 

 light emitted from a card which, after hav- 

 ing been exposed to daylight of moderate 

 intensity for two hours, had been in total 

 darkness for twenty-six hours. The paint 

 appears to be of satisfactory durability as 

 against all weathers and the action of sea- 

 water. The useful purposes to which it 

 may be applied are almost innumerable. 

 Clock-faces painted with it will show the 

 time ; match-boxes can be found, all through 

 the night ; the roofs of railway-cars will light 

 passengers through tunnels ; buoys in har- 

 bors and channels, and life-buoys, can be 

 made visible ; ships may show themselves to 

 each other in the darkness ; the diver, paint- 

 ing his dress with it, may be his own lantern 

 and carry enough daylight with him to en- 

 able him to work under water at a consid- 

 erable advantage. Its application to use 

 in powder-magazines and coal-mines, and 

 wherever fire-lights are dangerous, may be 

 considered as among the things that are 

 practicable. The manufacturers of the 

 paint, Messrs. Ihlee & Home, of Alderman- 

 bury, London, say that it now costs twenty- 

 eight shillings, or about seven dollars, a 

 pound, and that a pound of it will paint 

 about twenty-eight square feet. Two years 

 ago they held it at five guineas a pound, but 

 they have been able to lower the price grad- 

 ually, and hope ultimately that it may be 

 afforded at less than the cost of white-lead. 



Is South America rising or sinking ? 



The question whether the South American 

 Continent is sinking or not is one on which 

 considerable difference of opinion still exists. 

 Professor Orton several years ago expressed 

 the belief that the barometric observations of 

 the heights of the principal mountains, which 

 have been continued through more than a 

 hundred years, afforded evidence of a gradual 

 sinking, and this opinion has prevailed exten- 

 sively. Professor Agassiz believed that the 

 eastern coast was sinking while the western 

 coast was rising, and Darwin infers, from the 

 discovery of the remains of an ancient civili- 

 zation on lands that are now too high for the 

 development of human life, that the land is 



