May 19, 1870] 
NATURE 
57 
very much greater than any estimate which our present know- 
ledge allows us to accept for the heat of combination of zinc 
and copper. For something much less than the thermal equiva- 
lent of that amount of energy would melt the zine and copper ; 
and, therefore, if in combining they generated by their mutual 
attraction any such amount of energy, a mixture of zinc and 
copper filings would rush into combination (as the ingredients 
of gunpowder do) on being heated enough in any small part of 
the whole mass to melt together there. Hence we may infer 
that the electric attraction between metallically-connected plates 
of zinc and copper of only zpyata000 Of a centimetre thickness, 
at a distance of only z55p¢0000 Of a centimetre asunder, must 
be greatly less than that calculated from the magnitude of the 
force and the law of its variation observed for places of measur- 
able thickness, at measurable distances asunder. In other words, 
plates of zinc and copper so thin as a four-hundred-millionth 
of a centimetre from one another, form a mixture closely 
approaching to a molecular combination, if, indeed, plates so 
thin could be made without splitting atoms. Wishing to avoid 
complication, I have avoided hitherto noticing one important 
question as to the energy concerned in the electric attraction of 
metallically connected plates of zinc and copper. Is there not 
a change of temperature in molecularly thin strata of the two 
metals adjoining to the opposed surfaces, when they are 
allowed to approach one another, analogous to the heat pro- 
duced by the condensation of a gas, the changes of tempera- 
ture produced by the application of stresses to elastic solids 
which you have investigated experimentally, and the cooling 
effect I have proved to be produced by drawing out a liquid 
film which I shall have to notice particularly below? Easy 
enough experiments on the contact electricity of metals will 
answer this question. If the contact-difference diminishes as 
the temperature is raised, it will follow from the Second Law 
of Thermodynamics, by reasoning precisely corresponding with 
that which I applied to the liquid film in my letters to you of 
February 2nd and February 3rd, 1858,* that plates of the two 
metals kept in metallic communication and allowed to approach 
one another will experience an elevation of temperature. But 
if the contact difference increases with temperature, the effect 
of mutual approach will be a lowering of temperature. On 
the former supposition, the diminution of intrinsic energy in 
quantities of zinc and copper, eat a on mutual approach 
with temperature kept constant, will be greater, and on the 
latter supposition less, than I have estimated above. Till the 
requisite experiments are made, further speculation on this 
subject is profitless : but whatever be the result, it cannot in- 
validate the conclusion that a stratum of sppptuoan Of a centi- 
metre thick cannot contain in its thickness many, if so much 
as one, molecular constituent of thé mass. Besides the two 
reasons for limiting the smallness of atoms or molecules which 
Ij have now stated, two others are afforded by the theory of 
capillary attraction, aud Clausius’ and Maxwell’s magnificent 
working out of the Kinetic Theory of gases. In my letters to 
you already referred to, I showed that the dynamic value of the 
heat required to prevent a bubble from cooling when stretched 
is rather more than half the work spent in stretching it. 
Hence, if we calculate the work required to stretch it to any 
stated extent, and multiply the result by $, we have an 
estimate, near enough for my present purpose, of the augmen- 
tation of energy experienced by a liquid film when stretched 
and kept at a constant temperature. Taking ‘o$ of a gramme 
weight per centimetre of breadth as the capillary tension of a 
surface of water, and therefore "16 as that of a water bubble, 
I calculate (as you may verify easily) that a quantity of water 
extended to a thinness of ssyyhuaaw Of a centimetre would, 
if its tension remained constant, have more energy than the 
same mass of water in ordinary condition by about 1,100 
times as much as suffices to warm it by 1° Cent. This is more 
than enough (as Maxwell suggested to me) to drive the liquid 
into vapour. Hence if a film of sspctuss0 Of a centimetre 
thick can exist as liquid at all, it is perfectly certain that there 
cannot be many molecules in its thickness. The argument from 
the Kinetic Theory of gases leads me to quite a similar con- 
clusion. i 
April 19.—Annual meeting, Dr. J. P. Joule, F.R.S., Presi- 
dent, in the chair. The report of the council having been read, 
the following gentlemen were elected officers of the society for 
the ensuing year :—President : E. W. Binney, F.R.S., F.G.S. ; 
Vice-presidents : Dr. J. Prescott Joule, F.R.S., Dr. E. Schunk, 
* Proceedings of the Royal Society for April, 1858. 
F.R.S., Dr. R. Angus Smith, F.R.S., Rev. W. Gaskell, M.A. ; 
Secretaries: Dr. H. E. Roscoe, F.R.S., &c., J. Baxendell, 
F.R.A.S. ; Treasurer: T. Carrick ; Librarian: C. Bailey. Of 
the Council: P. Spence, F.C.S., G. Venables Vernon, F.R.A.S., 
J. B. Dancer, F.R.A.S., W. Leeson Dickinson, H. Wilde, R. 
Dukinfield Darbishire, F.G.S. A paper on ‘‘Infant Mortality 
in Manchester” was read by Mr. J. Baxendell, F.R.A.S., who 
combated the assertion that the high death-rate of Manchester 
and other towns in the cotton manufacturing districts is due 
to the mortality among infants and young children being 
relatively much greater than in large towns in other parts of the’ 
country, a careful examination of the mortality returns showing 
that a much larger proportional number of deaths of infants and 
young children takes place in other towns, where the general 
death-rate is decidedly lower. 
CAMBRIDGE 
Cambridge Philosophical Society, May 2.—Clement Hig- 
gins, B.A., Downing College, was elected a fellow. Com- 
munications :—By Professor Miller, F.R.S.: ‘‘On the best 
form for the ends of measures d@ doués.”’ The author found that 
the best form was that of two ‘knife edges,’ whose edges were 
in planes perpendicular to each other, and were not straight 
lines, but arcs of circles, whose centre was the opposite end of 
the axis of the bar. With this form the error (/ being length of 
bar, and ¢ distance between real and assumed position of the 
A 
point where the axis intersects the bounding surface) <7 
while in the forms commonly used it was either - or = 
By Mr. Bonney (St. John’s College): Note on supposed 
Molluse Borings in the limestone of Derbyshire. The author 
first described a large number of burrows which he had examined 
in the hills above Matlock ; these were generally directed up- 
wards, and too irregular in form to be PAol/as burrows, as had 
been asserted ; he then described some burrows observed in a 
scarp of limestone about nine feet above the stream in Miller’s 
Dale, by the road-side. He believed this scarp tobe artificial ; but 
whether so or not, the gorge was most distinctly one of fluviatile 
erosion, and he maintained that this case was fatal to the 
Pholas theory. He considered the burrows to be the work of 
Lelices. 
BRIGHTON 
Brighton and Sussex Natural History Society, April 
14.—Mr. Glaisher, Vice-president, in the chair. A com- 
munication from Mr. Gwyn Jeffreys respecting the Sars 
testimonial, was read by the Hon. Sec., after which a 
subscription was made among the members present, the 
Society not having power to vote its own funds for such a 
purpose. Mr. T. H. Hannah, the President, read a report on 
** Soundings made by Sir (Captain) E. Parry in 1818.” These 
soundings were purchased some years since among the geological 
specimens of Sir E. Parry, from his widow, by Mr. J. Cordy 
Burrows, of Brighton, who deposited the geological specimens in 
the Brighton Museum, and gave the soundings to Mr. Peto. 
The discoveries of last year giving a prominence to sea-soundings, 
they were placed in January in Mr. Hannah’s hands to examine 
microscopically, and report on their contents to the society. 
The soundings were made in Davis's Straits, and Lancaster 
Sound between 68° and 71° 15’ N. lat. and 73° and 78° 34’ W. 
long. at depths between 22 fathoms and 1,058 fathoms. Those 
under 58 fathoms contained nothing but stones and corals, some 
of the stones had evidently been rubbed by the action of a 
strong current ; those from 201 fathoms were much less disturbed 
and consisted chiefly ofa sandy material; from 674 fathoms 
there was an almost absence of inorganic débris, showing the 
non-existence of currents, and plenty of the testa of 
arenaceous foraminiferze. In all the deep ones diatomaceze were 
very beautiful, as well as sponge spicules and arenaceous 
foraminiferze ; but polycystinee and cretaceous foraminiferz 
were but sparsely found. He had also met with casts similar to 
those found in the greensand, and some highly organised 
spicules which he had not yet identified. At one of the micro- 
scopical meetings the slides would be exhibited. He much re- 
gretted they were not examined earlier, as they would then have 
preceded the discoveries of Carpenter and others, who, by the 
deep-sea soundings recently made, had opened out new ideas of 
life at great depths. Reference was then made to what had 
been done by Carpenter, Jeffreys, Thomson, and others 
in adding to our knowledge of the conditions of existence 
