[82 ] 
for his Obfervations. In this Box was a little Win- 
dow, in which a cylindrical Tube was fitted fo ex- 
actly, that no Light could be admitted but through 
the Tube, in which there was an Apparatus fo 
adapted, that the Perfon within could place any Ob- 
ject proper for Obfervation in fuch a Manner, as to 
receive as much Light as it could contain, and then 
to turn it inftantly towards his Eye, without admiting 
the leaft Ray of Light, befides that brought in by 
the Object. The Infide of this Box muft be abfolutely 
dark ; without which Caution many of the Attempts 
would be unfuccefsful ,• becaufe the Light in many 
of the Subjects was neither very lively nor very laft- 
ing. Therefore it was neceffary alfo, that the Eyes 
of the Obferver Ihould be as free as pofiible from 
the Impreffions of former Vifion : So that it were 
proper to make thefe Obfervations immediately after 
Sleep, or to keep the Eye you intend to make ufe 
of fhut at leaft half an Hour before you enter the 
Box. A Proof to know whether your Eye is pro- 
perly difpofed, will be expofing a Piece of white Pa- 
per to the Light in the Tube, and then being able to 
perceive its Form and Colour when turned towards 
you in the Box. 
Our Author divides the Phofphori into feveral 
Kinds ; fome of which Ihine of themfelves naturally, 
as the Glow worm and Dates 5 or adventitioufly, as 
the Flcfh of Animals, which moft probably arifes 
from a Degree of Putrefaction, fometimes too flight 
to be obvious to our Senfes. Other Bodies become 
luminous by Attrition, Heat, the free Accefs of Air, 
and, laftly, by imbibing and retaining the Rays of 
Light. Thofe Bodies that are luminous by Attrition, 
3 
