On the Atomic Philosophy. 137 
in the system, is not by emitting or radiating its own substance 
(a rude unphilosophic idea), but a change it produces in the elec- 
trical relations of all ponderable matter, already united with 
fluidium ; which changes always produce heat and light, in pro- 
portion to the intensity of the action. This will also account in 
a satisfactory manner, why the moon should afford us light, but 
not heat. Fluidium, in its passage from one lunar ponderable sub- 
stance to another, produces heat and light, the heat is absorbed 
iby the receiving body, and as the cause is perpetual, so wili be 
the effect : we feel no heat, but the light will be without inter- 
mission. 
On the Tides. 
Since my Essays went to press, I have turned over the Asiatic 
Researches, and had great satisfaction in finding a very remark- 
able confirmation of my theory; viz. that the tides are not pro- 
duced by the influence of the sun and moon unitedly or separately, 
but by the diurnal motion of the earth: see Observations on the 
Barometer, by Dr. Balfour and Mr, Farquhar, 4th vol. Asiatic 
Researches, Calcutta 1794. 
“‘ Ist. ‘That in the interval between 10 o’clock at night and 
six in the morning, there existed a prevailing tendency in the 
mercury to fall. 
‘¢ 2d. That in the interval between 6 and 19 in the morning, 
there existed a prevailing tendency in the mercury to rise. 
¢ 3d. That in the interval between 10 in the morning and 6 
in the evening, there existed a prevailing tendency in the mer- 
cury to fall. 
* 4th. That in the interval between 6 and 10 in the evening, 
there existed a prevailing tendency in the mercury to rise. 
‘That there exists a law in nature, by which the mercury of 
the barometer, let the standing weight be what it may, is liable 
to the effects of a constant and regular periodical diurnal! fluctu- 
ation. : 
* The periods are evidently connected with the earth’s diurnal 
motion ; and, if we had no satellite, might easily be explained by 
the atmospherical.tides caused by the sun. But when we find that 
the barometer is not in the least observable degree affected by 
the moon’s passage over the meridian, or by the united action of 
the sun and moon at the syzygies, we have absolute proof that 
this cannot be the cause: neither can the expansion of the mer- 
cury, being directly opposite to the phenomena, the greatest de- 
gree of heat taking place at 3 o’clock, when the mercury is 
lowest. The observations were taken every half hour during a 
complete lunation.” 
Josep Luckcock. 
XXII. On 
