88 
HalLj on Paraffin Oils. 
lamp before a concave reflector, and the light being then 
passed through a narrow slit in a sheet of cardboard, in front 
of which was a prism, the prismatic ray was received on a 
sheet of white paper, and the purity and breadth of colour 
between the red and blue rays noted as shown in the table. 
The second was by removing the lamp from the microscope 
after a bee^s tongue and a micrometer were brought into 
focus with a one-fourth objective and a B eye-piece, and mea- 
suring the distance when it became impossible to count the 
rings of the first, or the lines of the second. The remaining 
lines of the table give the length of carbonized wick after 
each period of burning, the quantity of oil consumed in each 
trial, the temperature of the room, the specific gravity of each 
sample of oil, and the temperature at which it permanently 
ignited on water, the total result showing that "Young's 
Paraffin" is the best material for a microscopical lamp of the 
three oils examined. 
Young's Paraffin. 
Price's Belmoiitine. 
Diamond Crystal 
OU. 
1st Trial. 
2ndTrial. 
1st Trial. 
2DdTrial. 
1st Trial. 
2nd Trial. 
Character of light with^ 
prism, and width of 
band between the red 
and blue 
\ 
\ 
1 
1 
Clear 
and 
bright 
After 
6 
hours 
20 feet 
6 
hours 
25 inch 
3| oz. 
55° 
826 
^5 inch 
After 
hour 
22 feet 
8ft.3in. 
hours 
id i"ch 
Ifoz. 
58° 
823 
165° 
1 
Very 
dirty 
and 
dull 
After 
6 
hours 
8 feet 
6 
hours 
25 inch 
3| oz. 
55° 
816 
inch 
After 
hour 
8f,.6in. 
3ft.6in. 
2i 
hours 
^oif^ch 
If oz. 
58° 
815 
160° 
Not so 
dull 
as the 
last. 
After 
6 
hours 
10 feet 
6 
hours 
25 inch 
4| oz. 
55° 
810 
inch 
After 
hour 
11 feet 
5 feet 
2 
hours 
lo inch 
If oz. 
58° 
810 
124° 
Distance at which a^ 
microscopical object 
became indistinct by 
direct light 
Bee's tongue 
Micrometer 1000 inch. . . 
Carbonized (black)length 
of wick 
Quantity consumed 
Temperature of room ... 
Specific gravity (hydro- ' 
meter graduated for 
60°) 
Temperature of perma- " 
nent ignition on water . 
