Journal

ciple certainly ought not to be overlooked; though perhaps Mr. Wenham and others who may be trying to extend our optical resources, may think that in saying the neglect of the principle might (in microscopic phrase) occasion "loss of time," Dr. Pigott is, to say the least, putting it very mildly.

Of Dr. Pigott's mathematical knowledge we may form an estimate from his idea that knowing the ratio which the sine of an angle bears to the sine of another given angle, we cannot find the former angle without having recourse to logarithms. For some of his other errors we ought, perhaps, to hold the printer responsible; but what will the Civil Service examiners say to the following exercise in decimals (and there are many of the same kind " carefully calculated ”) :—The number 1.336 is to be divided by 1.500, and the answer given is 0.890666; that is to say, Dr. Pigott believes that two expressions true to three decimal places only, can be made to yield a quotient true to six places.

The only tangible result from these papers is the suggestion that the greater brilliancy of water lenses is in one case due to the fact that more of the pencil of light is lost in the air lens than in the other from total reflexion. This many persons may not have observed, though self-evident when once attention is called to it. Mr. Wenham indeed had already* ascribed the superiority in part to the smaller loss of light from reflexions; but I think that he there had only the general case in view. Dr. Pigott's remark applies only when the object is artificially mounted (in balsam or some such medium). When the object is in its natural state, either lens transmits the full pencil; but in this case, too, the immersion lens would lose somewhat less light than the other by ordinary reflexions; and from the manner in which Mr. Wenham expresses himself it seems likely that it was only this general case he had in view in the passage referred to.

I hope that nothing I have said in this letter may seem unduly controversial. It is scarcely possible indeed to criticize such papers without some appearance of this kind. Dr. Pigott has come forward not only as the censor of all existing object-glasses, but also as the possessor of improvements which for some unexplained reason seem still to be kept back as secrets. In such a case the only means left us of guessing at the value of what is kept back is by examining the value of what has been published.

Your obedient servant,

S. LESLIE BRAKEY.

* In the June No., p. 303.

PROCEEDINGS OF SOCIETIES.*

ROYAL MICROSCOPICAL SOCIETY.

KING'S COLLEGE, September 26, 1870.

The Session will commence on Wednesday, the 12th inst., and meetings held on the second Wednesday in each month, at 8 o'clock P.M., as usual.

On the 12th inst. the following papers will be read by Dr. G. W. Royston-Pigott, M.A. :

1st. "On Aplanatic Illumination."

2nd. "On Aplanatic Definition, with Optical Illustrations."

WALTER W. REEVES.

Assist. Secretary.

QUEKETT MICROSCOPICAL CLUB.†

At the ordinary meeting held at University College, August 27th, 1870, Dr. Lionel S. Beale, F.R.S., President, in the chair, seven new members were elected, four gentlemen were proposed for membership, a number of donations to the library were announced, and 113 slides were presented to the cabinet. A paper was read by Mr. T. C. White "On Papers for the Club," in which he offered a variety of suggestions as to the kind of papers it was most desired to obtain, and urged those members who had hitherto been working at subjects in silence to give to their fellow-members the results of their personal experiences by short practical communications at the meetings. Mr. Curties communicated to the meeting an interesting letter received from Mr. Davis, describing some remarkable eggs of insects which had been found parasitic upon the Black Peacock in the collection of the Zoological Society. The subject was illustrated by some very beautifully-executed drawings, and by a number of photographs presented by Mr. Davis for distribution amongst the members. Mr. M. C. Cooke exhibited to the meeting a photograph of the appearance of a portion of Pleurosigma angulatum, magnified 98,000 diameters, as shown at the Bailey Microscopical Club in New York, and of which a description has been read at the preceding meeting. It appeared, however, upon inquiry that the photograph was not taken from the object, but from a plaster representation of it. The Secretary read a letter from Mr. C. H. Sterne, of Liverpool, inviting the co-operation of the members on the occasion of the Soirée of the British Association to

* Secretaries of Societies will greatly oblige us by writing their reports legibly --especially by printing the technical terms thus: Hydra-and by "underlining words, such as specific names, which must be printed in italics. They will thus secure accuracy and enhance the value of their proceedings.-ED. M. M. J. † Report furnished by Mr. R. T. Lewis.

be held at St. George's Hall on September 22nd. Votes of thanks were unanimously passed to those gentlemen who had read papers, and the proceedings terminated as usual with a conversazione, at which a number of beautiful and interesting objects were exhibited, and a quantity of unmounted specimens, &c., were presented for distribution amongst the members by Messrs Archer, Coke, and Hainworth. Degeeria domestica-found for the third time in Britain, was exhibited alive by Mr. Oxley, and Mr. Curties showed specimens of the eggs of bird parasites both in their wet and dry conditions.

BIBLIOGRAPHY.

Annales musei botanici. Lugduno-Batavi. Edidit Prof. Dr. F. A. Miquel. Tom. IV., fasc 8 and 9, qr. fol. Leipzig. Fleischer.

Lehrbuch der Zoologie. Herren B. Altum. H. Landois. Freiburg. Herder.

Ueber Bewegungserscheinungen der Zellen. N. Leiberkühn. Marburg. Elwert.

Das Inulin. Ein Beitrag zur pflanzenphysiologie. K. Prantl. München. Kaiser.

Charles Darwin et ses précurseurs français. Étude sur le ransformisme. A. de Quatrefages. Paris.

Studien über das centrale Nervensystem der Wirbelthiere. L. Stieda. Leipzig. Engelmann.

Disease Germs; their supposed nature. Lionel Beale, F.R.S. London. Churchill.

Manual of Human and Comparative Histology. Edited by S. Stricker. Vol. I. Translated by H. Power, M.B. New Sydenham Society. London.

Elementary Course of Botany: Structural, Physiological, and Systematic. By Professor A. Henfrey. 2nd Edition, by Maxwell T. Masters, M.D., F.R.S. London. Van Voorst.