[October, 
Progress in Science. 
tial energy. Why two masses of matter possess potential energy when 
separated, in virtue of which they are conveniently said to attract one another, 
was still one of the most obscure problems in physics. If the ingenious idea 
of the ultramundane corpuscles, the outcome of the life-work of Le Sage, and 
the only even apparently hopeful attempt which has yet been made to explain 
the mechanism of gravitation was true, it would probably lead us to regard all 
kinds of energy as ultimately kinetic. A singular quasi-metaphysical argu- 
ment might be raised on this point, of which he could give only the barest 
outline. The mutual convertibility of kinetic and potential energy showed 
that relations of equality, though not necessarily of identity, could exist 
between the two, and thus that their proper expressions involved the same 
fundamental units, and in the same way. Thus, as we had already seen, that 
kinetic energy involved the unit of mass and the square of the linear unit 
diredtly, together with the square of the time-unit inversely, the same must 
be the case with potential energy ; and it seemed very singular that potential 
energy should thus essentially involve the unit of time if it did not ultimately 
depend in some way on energy of motion. In defence of accuracy, which 
was the sine qua non of all science, we must be “zealous,” as it were, even to 
“slaying.” And, as all the power of the Times would not compel us to put a 
y instead of an e into the word chemist, so neither would the bad example of 
Germany and France, though recommended to us with all the authority which 
might be attributed to an ex-president of the Association, succeed in inducing 
us to attach two or more perfectly distindt and incompatible scientific mean- 
ings to that useful little word, “ force,” which Newton had once and for ever 
defined for us with his transcendent clearness of conception. 
The usual Ledture to Working Men was delivered by Lieut. Cameron, 
R.N., C.B., on his “ Recent Journey across Africa.” 
The Mathematical and Physical Sedtion was presided over by Professor Sir 
William Thomson, F.R.S. His opening address was mainly devoted to a 
review of evidence regarding the Physical Condition of the Earth ; its Internal 
Temperature; the Fluidity or Solidity of its Interior Substance; the Rigidity, 
Elasticity, Plasticity of its External Figure; and the Permanence or Variabi- 
lity of its Period and Axis of Rotation. He first, however, referred to his 
recent visit to America. In the United States Government part of the Great 
Exhibition of Philadelphia, Prof. Hilgard showed him the measuring rods of 
the United States Coast Survey with their beautiful mechanical appliances for 
end measurement, by which the three great baselines of Maine, Long Island, 
and Georgia were measured with about the same accuracy as the most accu- 
rate scientific measures whether of Europe or America have attained in com- 
paring two metre or yard measures. In the United States telegraphic depart- 
ment he saw and heard Elisha Gray’s splendidly worked-out eledtric telephone 
actually sounding four messages simultaneously on the Morse code, and 
clearly capable of doing yet four times as many with very moderate improve- 
ments of detail ; he also saw Edison’s automatic telegraph delivering 1,015 
words in 57 seconds; this done b}' the long-negledted eledtro-chemical method 
of Bain, long ago condemned in England to the helot work of recording from 
a relay, and then turned adrift as needlessly delicate for that. In the Canadian 
department he'Jheard “To be or not to be — there’s the rub,” through an eledtric 
wire; but, scorning monosyllables* the eledtric articulation rose to higher 
flights, and gave him passages taken at- random from the New York newspapers 
with unmistakable distinctness by the thin circular disc armature of a small 
eledtro-magnet. The words were shouted with a clear and loud voice by 
Prof. Watson at the far end of the line, holding his mouth close to a stretched 
membrane, carrying a little piece of soft iron, which was thus made to perform 
in the neighbourhood of an eledtro-magnet in circuit with thieline motions pro- 
portional to the sonorific motions of the air. This, the greatest by far of all 
the marvels of the eledtric telegraph, was due to a young countryman of our 
own, Mr. Graham Bell, of Edinburgh and Montreal, and Boston. Who could 
but admire the hardihood of invention which devised such very slight means 
