PHONOGRAPHY 



PHOSPHORESCENCE 



143 



means of furnishing a record of communications 

 through the telephone. Phonographic clocks, 

 books, ami other devices have also been invented by 

 Mr Edison, whose discovery is evidently of a generic 

 nature, opening up a large and entirely new Held 

 in the arts and sciences. See also TELEPHONE. 



Phonography. See SHORTHAND. 



Phonolite. See CLINKSTONE. 



I'lio r mill in. See FLAX (NEW ZEALAND). 



Phosphates. See PHOSPHORUS, MANURE. 



Phosphatic Diathesis, in Medicine, desig- 

 nates the condition in which there is a tendency in 

 the Urine (q.v.) to deposit white gravel. 



Phosphorescence. Strictly speaking, the 

 term is applied to the phenomenon, exhibited by 

 certain bodies, of remaining luminous in the dark 

 for some time after being exposed to a strong light. 

 Certain preparations, such as calcium sulphide 

 (see Lr.Mixors PAINT), indurated limestone, &c., 

 possess this property in a very high degree. With 

 the great majority of phosphorescent bodies, how- 

 ever, the duration of the phenomenon is very 

 short, rarely more than a small fraction of a second. 

 Becquerel, who studied this phenomenon with great 

 care, invented a very ingenious instrument for the 

 purpose, called a n/ioujthoroscmie. The Inxly to be 

 tested is placed in a small drain, which nas an 

 opening at each end. In this drum there revolve 

 two discs, mounted on the same axle, and pierced 

 symmetrically with the same number of holes. 

 They are so adjusted that when a hole in one disc 

 is opposite to the hole in the corresponding end of 

 the drum the second disc closes the hole at its end 

 of the drum, and rice versa. Light is admitted by 

 one of the holes in the drum so as to fall on the 

 object, and it is examined through the other hole. 

 It if) obvious that, when the discs are made to 

 revolve, the object is alternately exposed to light 

 and presented to the eye. By a train of multiply- 

 ing wheels, these alternations may be made to suc- 

 ceed each other as rajiidly as the oliserver |>leases, 

 and thus the object is presented in the dark to his 

 eye as soon after its exposure to light as may l>e 

 debited. Almost all boUM arc found to lie plcos- 

 phorescent ; for instance, some kinds of pink rubies 

 when e.\]iOHi>il to sunshine in this apparatus appear 

 to glow like live coals in the dark. When phos- 

 phorescence is continuous, l>odies receiving light 

 and giving off radiation of a lower refningibility, 

 we have the phenomenon olerved by Brewster and 

 lleisehe.! in quinine and certain crystals of fluor- 

 spar, and thence called /'/ nm->: irence. The green 

 colouring matter of leaves, A decoction of the bark 

 of the horse-chestnut, and the common can/->/ glass 

 (coloured with oxide of uranium (are bodies which 

 exhibit this phenomenon very well. Perhaps the 

 must -.triking method of studying the phenomenon 

 i to receive in a darkened room the solar Sped HUM 

 (q.v.) on r, sheet of white paper, and to pass over 

 the coloured spaces a brush dipped in a solution 

 of sulphate of quinine with sulphuric acid. No 

 chang" is produced on the less refrangible rays, 

 but in the Mue and indigo spaces a strange change 

 of colour is at once apparent where the liquid has 

 !>< m spread. This appears more strongly in this 

 violet, and vividly in tin- spaces beyond the violet, 

 when- rays fall which excite no luminous sensation 

 in the eye. By this experiment the visible length 

 of the spectrum may easily In- doubled. By using 

 the electric light, which is peculiarly rich in these 

 highly-refrangible rays, a prism of <|iiartz, which 

 allows them to pass very freely, and various fluores- 

 cent substances. Stokes has obtained spectra six or 

 eight times as long as those otherwise visible. The 

 'ri-Hic of all these rays is that they are less 

 refrangible than those froni which they are pro- 



duced. The entire phenomenon is, as Stokes first 

 showed, identical in principle with Leslie's photo- 

 meter, in which light was measured when changed 

 into heat by absorption in the coloured glass, of 

 which one of the bulbs of his differential ther- 

 mometer was formed. Ordinary phosphorus (from 

 which the phenomenon took its name) becomes 

 luminous in the dark by slight friction ; whence 

 the common trick of drawing self luminous figures 

 on doors and walls with a stick of phosphorus, or 

 an ordinary lucifer match wetted. 



PHOSPHORESCENCE IN ORGANIC BEINGS. The 

 emission of light by minerals after insulation and 

 the cognate phenomena of luminosity on heating, 

 friction, cleavage, crystallisation, &c. are of quite 

 different nature from the production of light by 

 organisms, the special subject to which we now turn. 



f./liiiiini.-iitif (file to Putl'ffnrtinii w lu Dim'tim'. 



The fact that many organic subsi.inces (especially 

 fish) Ijecome luminous when decaying has long 

 been known, and has often been erroneously ad- 

 duced as the chief cause of the phosphorescence of 

 the sea. It is only quite recently that the dis- 

 covery of luminous bacilli has rendered possible 

 any general explanation of these facts, and even 

 yet its wide applicability remains to be proved. 

 They have been shown to exist in several instances 

 which will be mentioned below, and the constant 

 association of these low forms of life with putrefac- 

 tive processes ai mice suggests the hypothesis that 

 luminosity under such circumstances may be due 

 to their presence. Perhaps they may also account 

 for the few instances in which t he human body has 

 been recorded as phosphorescent during life. 



Luminosity of IJeatt/iy Living Organisms. (1) 

 In the vegetable kingdom the instances of the 

 occurrence of this property are but few, and the 

 majority of these belong to the alga- and fungi, the 

 bacilli or bacteria al>ove mentioned being referable 

 to the former. Most of the fungi are Hymenomy- 

 cetea (Agaricm, spp. ) : in some cases the mycelium 

 (root-like threads) gives out the light; in others, 

 as in .1. olearius, not uncommon at the roots of 

 olive-trees, it is the under surface of the mushroom- 

 like head. The light is only seen while growth j 

 progressing ; it ceases so soon as the Fungus is 

 mature. A moss ( Mi istostega umii-undacea), some 

 grasses, a Euphorbia (K. phoxpltorea), a lily 

 (Lilimn bulbiferum), a poppy (Pu/iarer oriottale), 

 and a nasturtium (Tropaolwn majitt) have all 

 been recorded as luminous. The last instance is 

 worthy of note as having been observed by the 

 daughter of Limucus in 1762. 



(2) lu the animal world there is not one of the 

 larger groups, up to and including the fishes, which 

 does not afford some good examples of this pheno- 

 menon. A complete list of these would be outside 

 the scope of such an article as the present : it must 

 suffice to mention some of the best instances in 

 each class, indicating briefly the nature of the 

 photogenic mechanism. Among the Proto/oa the 

 small spheroidal Noctilitca miliuris is perhaps tin- 

 most widely spread instance of this property, this 

 organism, or others allied to it, abounding at cer- 

 tain times around the coasts of the greater part of 

 the woild. The light is emitted from the general 

 protoplasm of the body ; a pocket-lens shows SOUK; 

 points to be brighter than others, whilst a higher 

 magnifying power shows these to be really groups 

 of smaller points, just as a nebula is gradually 

 resolved into stars by increasing powers of the tele- 

 scope. On the high seas Noctiluca seems to be 

 replaced by species of Pyrocystis, one of the dis- 

 coveries of the Challenger expedition ; these may 

 possibly, however, be stages in the life-history of 

 very similar forms. Among the Porifera (sponges) 

 the only recorded luminous form is the larva of a 

 species of Keniera. The poverty of this class is, 



