On a new Transit Instrument. 105 
Secondly, by the collision of the flint and steel, the thermogen 
of the atmosphere is forced into union with the photogen of the 
metal. The combustion thus produced, melts the minute par- 
ticles of steel struck off by the flint into small globules. That 
this metal contains the generator of light is well known, by the 
burning of iron or steel wire in oxygen gas, 
Sparks are emitted when two quartz stones are struck smartly 
against each other under water; and Mr. Kirwan affirms, that 
sparks are produced by the collision of Aint and steel under com- 
mon spring water. 
That sparks are produced by the collision of flint and steel un- 
der water, I have no doubt, since water is a letter conductor of 
thermogen and photogen than almospheric air. And the sparks 
so produced, being intensely hot, cannot be extinguished by the 
water* as soon as they are generated. 
Experiment 8. From Count Rumford’s experiments it ap- 
pears, that by a moderate degree of friction the same piece of 
metal afforded so much caloric under water as to keep it boil- 
ing.—Phil. Trans. for 1798. 
This experiment may be explained on the same principle as 
the last. Water, being a better conductor of thermogen than 
atmospheric wir, cannot preyent the production of caloric by the 
collision or friction of hard bodies, 
Lynn, Feb. 4, 1814. Ez. WALKER. 
XXII, On Sir H. C. ENGLEFIELD’s new Transit Instrument. 
By the Rev. James Groosy. 
Cirencester, Feb. 4, 1814. 
ae OP receiving your last Magazine, I was not a little sur- 
prised to see in the new Transit Instrument there described, the 
exact representation of one I had thought of more than three 
years ago; a drawing and description of which I then sent to 
Mr. Banks, astronomical instrument-maker, &c. Strand, request- 
ing him to make me a transit upon that plan, unless he saw very 
good reasons to suppose it would not answer. He wrote to me 
in return, that he had well considered my plan, had shown it to 
several scientific gentlemen (among whom he particularly men- 
tioned Mr. Pond, the present astronomer royal), that they had 
all pronounced such a construction of the instrument. useless, 
and he therefore by all means recommended one on the old plan, 
and not to put myself to a needless expense about an instrument 
* When iron or steel wire is burnt in oxygen gas, the particles of metal 
which drop from the end of the wire will fuse the glazing of an earthen 
plate, after having passed through water_an inch deep. 
that 
