Mr Charles Bell on the Motions of the Eye. 371 
The calculations are made for the temperature which affords 
the greatest mechanical effect, —but a stranger to these matters 
would judge by the degree of vacuum that may be obtained in 
the cylinder. To show how far this may be done, we may con- 
sider the temperature of flame to be about 1050 degrees ; and 
in a small cylinder and with oil-gas, 1 have little doubt but that 
it might be filled with a jet of dame of that tempetature, if not 
of a much greater one ; but assuming t — 1050°, we have 
30^1 — — 20 inches of mercury. The advantage 
of this increase of moving force is, however, not so great as to re- 
pay the increased consumption of gas to produce it. The ex- 
change of steam-boilers for the retorts and gasometers of a gas- 
work, will certainly not be esteemed an advantage ; while, for 
a locomotive machine, the expence would be so great as to put 
it entirely out of question whether it would be better to carry 
oil-gas compressed into a 30th of its bulk, or to use a high-pres- 
sure engine. 
Art. XX . — On the Motions of the Eye. By Charles Bell, 
Esq. F, R. S. kc. Read before the Royal Society of Edin- 
burgh, March 21. 1825 
J N the march and progress of Science, as men choose to call 
that slow and painful advance which we make in knowledge, 
there seems to be a natural disposition to chide and hunt back 
whoever attempts to make a path for himself. While every one 
observes with complacency the improvement of the age, indivi- 
dual efforts meet with opposition almost amounting to enmity. 
To complain of this were about as wise as to lament any physi- 
cal and unavoidable annoyance. But it is my apology for en- 
croaching on the time of the Society. On any other account, I 
ought not to regret that I am brought back to the reconsidera- 
tion of a subject which is full of interest. 
Some papers of mine appeared in the Philosophical Transac- 
tions of Loiidon^ o\\ the Anatomy of the Nervous System; in 
which I found it necessary to make some observations on the mo- 
