1872.] Mathematical and Physical Science. 511 
theology and science are, where they touch, perfectly defined, while we shall 
certainly resent the endeavour he has made to place theology in supremacy 
to science in the investigation of the Laws of Nature, whatever we may do 
in investigation as to the Cause of those laws. 
The very attributes of science have been attacked by Dr. Carpenter; and 
whatever may be the issue of the matter, there remains the fad that he has 
placed himself under the necessity of more clearly stating his reasons for 
the attack. 
SECTION A.—MATHEMATICAL AND PHYSICAL SCIENCE. 
President.—Warren de la Rue, D.C.L., Ph.D., F.R.S., V.-P.R.A.S., V.-P.C.S. 
Vice-Presidents.—Prof. G. C. Foster, F.R.S.; F. Fuller; James Glaisher, 
FiR-S.; J. Norman Lockyer, F.R.S.; J. Phillips, F-R.S.; H. J..S. Smith, 
F.R.S.; W. Spottiswoode, F.R.S.; Sir W. Thomson, LL.D., F.R.S.; Sir 
Charles Wheatstone, D.C.L., F.R.S. 
Secretaries.—Prof. W. R. Clifford, M.A.; J. W. L. Glaisher, B.A., F.R.A.S.; 
Prof. A. S. Herschel, B.A., F.R.A.S.; G. F. Rodwell, F.R.A.S., F.C.S. 
The President opened the proceedings by stating that he would confine his 
attention to astronomical photography. He showed that, at the very outset, 
astronomical differs from ordinary photography, inasmuch as the image of the 
obje@ which falls upon the collodion film is always in motion. Strata of air 
are ever in motion between the plate and the object, and each of these strata 
causing refraction the result is a * flickering” image to be impressed upon the 
sensitive film, being a similar effect, from the same cause, of the appearance 
of the ‘‘ twinkling”’ of stars. Dr. de la Rue has observed that this flickering, 
at certain times, chances to be at a minimum, and it has been at such times 
that he has obtained his celebrated photographs of the moon. He then de- 
tailed the difficulties arising from the non-coincidence of the foci of the 
chemical and visual rays of light, from which it accrues that, if the prepared 
plate be placed where a visually well-defined object falls upon the film, the 
focus not being that of the chemical rays the best result is not obtained. Dr. 
de la Rue, to remedy this defect, employs a reflecting instead of a refracting 
telescope. Mr. Rutherford, of New York, on the contrary, employs a refracting 
telescope, but one in which special adjustments have been made. The rays of 
light from the heavenly bodies are not only refracted during their passage 
through the atmosphere, but are absorbed by floating particles, solid and 
liquid, this absorption amounting to, perhaps, two-thirds of the chemical rays. 
For these and similar reasons, it would appear advantageous that the British 
Association or the Royal Society should possess a permanent observatory, 
situated at a great elevation, in a climate as free as possible from cloud. The 
President of the Section detailed the successful experiments of Lord Lindsay 
and Mr. Rannyard, as to the question whether reflections from the back 
surface of the photographic plate played any part in the production of the 
fringes observed in some astronomical photographs. In these experiments 
plates of ebonite and non-actinic yellow glass were prepared, and it was 
soon found that the outer haze completely disappeared in the photographs 
taken on ebonite, while on the yellow glass plates it was much fainter than on 
ordinary white glass plates. A wetted black paper at the back of an unground 
plate greatly diminished the outer haze; and a yellow glass plate ground on 
both sides, the back coated with a black varnish, caused the outer haze to en- 
tirely disappear, showing the greatest part of photographic irradiation to be 
due to reflection from the second surface. 
The failure of photography to present truthful pictures of nebulz and comets 
was passed under consideration, and thought to be due to the variation in 
atmospheric currents and the interposition of aqueous and solid particles. In 
following up the consideration Prof. Zollner’s theory of the self-luminosity 
and train of comets was commented upon, the President inclining to the view 
that ele¢tricity may be demonstrated to be sufficient cause, provided it be 
* granted that electricity may be developed by the action of solar heat,—if not 
in the process of evaporation, at least in the mechanical and molecular dis- 
turbances resulting from it. In conclusion, Dr. de la Rue expressed a hope 
