LIGHT. 679 
points have the fame efFeCl on phofphorefcence as upon 
the eleCtric fluid. M. Deflaignes diftinguilhes two kinds 
of phofphorefcence ; the one tranfient, the other perma¬ 
nent. Amongft the firft we may ftate, that which takes 
place when a certain quantity of water combines with 
quick-lime; amongft the latter, that of rotten wood, and 
other organized fubftances in a ftate of putrefaction. It 
appeared important to determine whether the pholphoref- 
cence that takes place in thofe bodies, which become lu¬ 
minous when their temperature is fomewhat increafed, is 
owing to combuftion. M. Deflaignes made experiments 
in atmolpheric air, in oxygen gas, and in the torricellian 
vacuum, to afcertain this point; but he could perceive no 
difference in the intenfity of the light under the different 
circumftances, when the experiments were made on inor¬ 
ganic bodies; but the light of organic bodies was increafed 
in oxygen, from which the author concludes that fome 
part of this light in the latter is owing to combuftion. 
Thefe luminous organic bodies more particularly occu¬ 
pied his attention. He made experiments on frelh-water 
fifti, fea-fifti, and various kinds of wood. The refults 
have proved, that the phofphorefcence of each is a fpecies 
of combuftion, in which water and carbonic acid are pro¬ 
duced. The woody part, and mufcular fibre, do not un¬ 
dergo in thefe changes any effential alterations. The 
phofphorefcence of the wood is chiefly owing to a gluti¬ 
nous principle, that ferves to unite the woody fibres; and 
that of the fifti, to a gelatinous principle, which unites 
the mufcular fibres. M. Deflaignes endeavoured to explain 
the luminous appearance of the fea, and to fupport his 
reafoning by a numerous collection of faCts relating to 
fpontaneous phofphorefcence. He attributes the light of 
the fea to two caufes; firft, to the prefence of phofphoric 
animalcules, and the emanation of luminous matter pro¬ 
duced by them; and, fecondly, to the Ample prefence of 
this matter diffblved and mixed in the water, proceeding 
not only from thefe animalcules, but from mollufci, filh, See. 
Among luminous bodies the diamond is to be reckoned ; 
as fome diamonds are known to ftiine in the dark. But, 
on account of the feeblenefs of their fplendour, it is ne- 
ceflary for the perfon who is to obferve them, previoufly 
to ftay in the dark at leaft a quarter of an hour; that the 
pupil of the eye may be dilated and enlarged, and fo ren¬ 
dered capable of receiving a large quantity of the rays of 
light. M. du Fay has alfo obferved, that the eyes ought 
to be ftiut for this time, or at leaft one of them ; and that, 
in that cafe, the light of the diamond is afterwards only 
feen by that eye which has been ftiut. Before the dia¬ 
mond is brought into the dark room, it muft be expofed 
to the funlhine, or at leaft to the open daylight, to imbibe 
a fufficient quantity of rays; and this is done in one mi¬ 
nute, or even lefs ; eight or ten feconds having been found 
to furnifli as much light as a ftone is capable of receiving; 
and, when brought into the dark, its light continues about 
twelve or thirteen minutes, weakening all the while by infen- 
fible degrees. It is very remarkable, that, in bodies fo ex¬ 
tremely fimilar to each other as diamonds are, fome fliould 
have this property of imbibing the fun’s rays, and (hining 
in the dark, and that others (hould not; yet lo it is found 
to be by experiment, and the molt nearly refembling Itones 
lhall be found, one to have this property, and another to 
be deftitute of it; while many of the molt diflimilar have 
the property in common. There feems to be no rule, nor 
even the leaft traces of any rule, of judging, which dia¬ 
monds have, and which have not, this property ; their na¬ 
tural brightnefs, their purity, their lize, or their lhape, 
contribute nothing to it; and all that has betn yet difeo- 
vered of the leaft regularity among them, is, that all yel¬ 
low diamonds have this property. This is fuppoled to 
arife from their having moreiulphur in their compofition, 
and therefore illuminating more readily, or emitting a 
more vifible flame. 
It is not only the open fun-lhine, or open day-light, 
which gives to thefe diamonds the power of ftiining in the 
darkj they receive it in the fame manner even if laid un¬ 
der a glafs, or plunged in water or in milk. M. du Fay 
tried whether it was poflible to make the diamond retain, 
for any longer time, the light it naturally parts with fo 
foon ; and found, that if the diamond, after being expofed' 
to the light, be covered with black wax, it will ftiine in 
the dark as well fix hours afterwards as at the time it- 
was firft impregnated with the light. 
The imbibing light, in this manner, being fo nice a pro¬ 
perty as not to be found in feveral diamonds, it was not 
to be fuppoled that it would be found in any other (tones; 
accordingly, on trial, the ruby, the fapphire, and the to¬ 
paz, were found wholly deftitute of it; and among a large 
number of rough emeralds, one only was found to poflefs 
it. Such is the ltrange uncertainty of thefe accidents. 
All the other lefs-precious (tones were tried, and found 
not to poflels this property of imbibing light from tlie 
daylight or funftiine, but they all became luminous by the 
different means of heating or friCtion ; with this difference, 
that fome acquired it by one of thefe methods, and others 
by the other; each being unaffected by that which gave 
the property to the other. The diamond becomes lumi¬ 
nous by all thefe ways. Beccarius alfo difeovered that 
diamonds have the property of the Bolognian phofphorus, 
about the fame time that it occurred to M. du Fay. Com . 
Bonon. vol. ii. p. 276. M. du Fay likewife obferved, that 
the common topaz, when calcined, had all the properties 
of this phofphorus 5 and, purluing the difeovery, he found 
the fame property, in a great degree, in the belemnites, 
gypfum, limeftone, and marble; though he was obliged 
to diirolve lorne very hard fubftances of this kind in acids, 
before calcination could produce this change in them; 
and with fome fubftances he could not fucceed even thus; 
efpecially with flint-ltones, river-fand, jafpers, agates, and 
rock-cry ftal. 
In Sweden a very curious phenomenon has been ob— 
ferved on certain Jlowers, by M. Haggern, leCturer in na¬ 
tural hiftory. One evening he perceived a faint flafh of 
light repeatedly dart from a marigold. Surprifed at fuch 
an uncommon appearance, he relolved to examine it with 
attention ; and, to be allured it was no deception of the eye, 
he placed a man near him, with orders to make a fignal at 
the moment when he obferved the light. They both lav/ 
it conllantly at the fame moment. The light was molt 
brilliant on marigolds of an orange or flame colour; but 
fcarcely vifible on pale ones. The flafh was frequently 
feen on the fame flower two or three times in quick (uc- 
ceffion, but more commonly at intervals of feveral mi¬ 
nutes; and, when feveral flowers in the fame place emit¬ 
ted their light together, it could be obferved at a confi- 
derable diftance. This phenomenon was remarked in the 
months of July and Auguft at funfet, and for half an hour 
when the atmofphere was clear; but after a rainy day, or 
when the air was loaded with vapours, nothing of it vvas- 
feen. 
The following flowers emitted flafhes, more or lefs vi¬ 
vid, in this order: 1. The marigold, Calendula officinalis* 
2. Monk’s-hood, Tropaolum majus. 3. The orange lily, 
Lilium bulbiferum. 4. The Indian pink, Tagetes patula et 
ereEla. To dilcover whether fome little inleCts or phof¬ 
phoric worms might not be the caufe of it, the flowers 
were carefully examined, even with a microfcope, with¬ 
out any fuch thing being found. From the rapidity of 
the flafh, and other circumftances, it may be conjectured 
that there is fomething of electricity in this phenomenon 
alfo. It is well known, that, when the piftil of a flower 
is impregnated, the pollen burfts away by its elafticity, 
with which electricity may be combined. But M. Hag¬ 
gern, after having obferved the flafli from the orange-lily,,, 
the antheras of which are a confiderable fpace diftant from 
the petals, found that the light proceeded from the petals 
only ; whence he concludes, that this eleCtric light is caufed 
by the pollen, which, in flying oft', is fcattered on the pe¬ 
tals. Whatever be the caufe, the effeCl is lingular and 
highly curious. 
A fimilar phenomenon in refpeCl to the ftate of thav 
weather, 
