W. Crookes—Radiant Matter. 247 
lished twenty years ago, he describes the appearance of alumina 
as glowing with a rich red color in the phosphoroscope. Here 
‘0 millionth of an atmosphere = 0°00076 millim. 
1315°789 millionths of an atmosphere = __1°0 millim. 
1,000,000- at if = = 760°0 millims. 
° u tt as = 1 atmosphere. 
+ Nearly 100 years ago Mr. Wm. Morgan communicated to the Royal Society 
a Paper entitled Blectrical Sstecwicsente- sate to ascertain the Non-conducting 
: um, The following extracts from this Paper, 
which was published in the Phil. Trans. for 1785 (vol. Ixxv, p. 272), will be 
read with interest :-— 
“A mercurial gage about fifteen inches long, carefully and accurately boiled till 
every particle of air was expelled from the inside, was coated with tin-foil five 
to form a communication between the brass cap and the 
mercury, into which the gage was inverted) the coated end was applied to o 
conductor of an electrical machine, and notwithstanding every effort, ope 1e 
smallest ray of light, nor the slightest charge, could ever be procured in this 
exhausted n 
the experiment will not 
electric light became visible, and as usual of a green 
didn agua Ge praise cracked at its sealed end, and in conse- 
quence the external air, by being admitted into the inside, has gradually pro- 
