SOLAR 1'HOSPHORI. 109 



minute crystals of quartz ; most compound salts, when clear and 

 crystallized, particularly Glauber's nitre, and borax, were also 

 found to be phosphorescent ; of vegetable substances all (In- fari- 

 naceous and oily seeds, all the gums, and several of the resins, 

 the white woods, and vegetable fibre, cither in the form of paper 

 or linen ; also starch and loaf.sugar proved to be good phosphori, 

 after being made thoroughly dry, and exposed to the direct rays of 

 the sun. Sundry animal matters, by a similar treatment, were also 

 converted into good phosphori, particularly bone, either fresh or 

 calcined, sinew, glew, hair, horn, hooff, feathers, and fish shells. 

 The same property, he observed, might be communicated to rock- 

 chrysfal, and some other of the gems, by rubbing them against 

 each other, so as to roughen their surface, and then placing them for 

 some minutes in the focus of a lens, by which the rays of light wer 

 concentrated upon them at the same time that they were also mode- 

 rately heated. 



In the year 176S, Mr. Canton contributed some important facts 

 relative to solar phosphori, and communicated a method of prepar- 

 ing a very powerful one, which, after the inventor, is usually 

 called Canton's phosphorus. It is thus made : Calcine oyster- 

 shells in the open fire for half an hour ; then select the widest and 

 largest pieces, and mix them with flowers of sulphur in the pro- 

 portion of one part of the latter to three parts of the former ; pack 

 the whole closely in a crucible ; lute on a cover, and heat it pretty 

 strongly for one hour ; when the crucible has again become quite 

 cold, turn out its contents, and select the whitest pieces for use. 

 Mr. Canton affirms, that hU phosphorus, inclosed in a glass flask, 

 aud hermetically sealed, retains its property of becoming luminous 

 for at least four years, without any apparent decrease of activity. 



Mr. Wilson found that a much greater brilliancy of colour 

 would be produced by letting the oyster-shells come in direct con- 

 tact with the burning coals, or other inflammable matter, and bj 

 being covered with it ; and that if the covering matter be iron, the 

 luminousness will be very bright ; if steel, still brighter and more 

 iridescent ; but if plates of charcoal , most so of all. 



If a common box smoothing-iron, heated in the usual manner, 

 be placed for half a minute on a sheet of dry, white paper, and the 

 paper be then exposed to the light, and afterwards examined in a 

 dark closet, it will be found that the whole paper will be luminous, 

 that part however on which the iron had stood being much more 

 shining than the rest. 



