DAR 
scaly aéted, to the beft of his meses in obedience 
to the didtates of juftice and religi 
us II]. named Gacon aignk was placed on 
a ftreggle ayainft the 
| of which will be found i in pe part of our work. 
e Maceponia and Persva. ius did not take the 
eomtind of his army in perfon till Alexander advanced into 
Cilicia. t him in all the pomp 
Rw, 
— 
n: Alexander went on in the 
gamela, Darius again fought, 
He now loft Babylon, 
weltering in his blood. Of Polyftratus, a Macedon nian, he be- 
fought a little water, which being brought to pares he defired 
* that his acknowledgments and thanks might convey~ 
ed to Alexander for his kindnefs and ere gual to his family, 
with an earneft exhortation that he would avenge his death 
on the traitors. Darius immediately eae his laft in the 
arms of Polyftratus. This was in the th year B.C 
being the 50th of the monarch’s age, and the 6th h of his 
. When his enemy a beheld his rival dead, 
m, to have rabies the body 
to be embalm 
terred with the remains of the Perfian mena. 
i 
See Camzra-Ob/cur 
hilofophy, are certain Gasnitone from 
A ia ee difcovered. They are not 
perceptible to our eyes, but they are manifefted by their 
effidis. Dr. Herfchel,‘and Mr. Ritter, are the difcoverers 
of thefe emarations. 
‘an 
Saal 
2K -CHA aes 
fities of heat in different parts o 
account of thefe invifible calor: fic rays will be found under 
the articles, Souar heat, and Rays of heat. 
re - May on pa continent, and, foon ee Dr. Wol- 
Jaft nown to each other, difcovered that 
the camiods folar a are accompanied with certain other 
47 
é 
DAR 
invifible rays qr emanations, which are only cognizable by 
their chemical aie ts upon certain fubftances, fuch as muriate 
a nitrate of filver. rays are more ea e than 
the violet rays of the coloured fpe&trum. r. T. Young, 
{peaking of thefe invifible rays of ee in a paper which is 
to be found in the Phil. carton rthe year 1803, fays, «* T 
“a of th 
cir refleGtion, from 
hrew this image on ae er ere in a folu- 
tion of Gace of filver, placed at the ditance of rakes nine 
inches from the miciofcope. In the courfe of an or= 
tions of three dark rings were very diftin@ly vifible, acl 
{mailer an the brighteft rings of the coloured, and coin- 
cidinz very nearly, in their dimenfions, mh the rings of 
violet light that appeared upon the interpofition of violet 
glafs. T thought the dark rings were a little {maller than 
the violet rings, but the rae was not fufficiently eter 
to be accurately afcertained ; it might be as much or 
yo_of the diameters, but ac reater. It is the lefs tur- 
prifing that the difference fhould be fo fmall, as the dimen- 
fions of the coloured rings do not by any means vary at the 
violet end of the {pe€trum, fo rapidly as at the red end.” 
It appears then, that the folar light confifts of three differ- 
ent emanations, or of three different kinds of rays; viz. the 
vifible coloured rays, the invifible calorific rays, and the in- 
vifible rays which are only difcermble by their chemical ef- 
ets upon certain fubftances. All thefe emanations are in- 
termixed with each other in the dire& rays of the fun; but, 
being aeubannl refrangible, they are feparated from each 
other by the fst and their prefence is manifefted by 
their peculiar Crore 
RK- Hh a po ortable camera obfcura, made not unlike 
a de ted with optic glaffles, to take profpeGs of 
lndleape, buildinge, fortifications, &c. See CamERA Oda 
parry 
“ 
“DARKEHMEN, in a gat a {mall town of Pruffia, 
i n Pru Me ich is called Lithuanian 
terburg remarkable for its 
woollen cloth aie end fora colony of Saltzbargh- 
ers, who fettled in the year 
KNESS means the se or the want of light. In 
common language we confider ourfelves as being in darknefs, 
whenever objets that dre pretty near to us, canno if 
tinguifhed from each other; but perfeét darknefs does not 
eafily occur; and it is owing to this that feveral animals 
can fee in what we eall darknefs ; viz, the eyes of thofe ani- 
mals are fo formed as to be able to fee with very little light. 
But it appears from the experiments of M. le Cat and others, 
mal it 
The i in nquiries concerning the nature of a are fo in- 
timately conneGted w 
propagat rough a peculiar fub- 
an eres Sifperted throughout ae univerfe. Whence 
of d m i 
bable, that light is a real fubftance thrown out in 7 a 
