NOTICES OF MEETINGS. II5 
NOTICES OF MEETINGS. 
MICROSCOPICAL SOCIETY OF LIVERPOOL.—The fourth ordinary 
meeting of the Thirteenth Session of this Society was held at the Royal Institu- 
tion, on Friday, April 1st, 1881; Dr. Carter, President, in the chair. 
The Hon. Sec. announced the donation of twelve microscopic slides from A, 
C. Cole, Esq., London, honorary member; and the Journal of the Quekett 
Club, from the club. One new member was elected, and two gentlemen were 
nominated for election. 
The President then called upon Mr. Mayall, Junr., F.R.M.S., for his com- 
munication on “ Brass and Glass.” 
Mr. Mayall said it might be in the recollection of many then present that 
about a year ago he had the honour of addressing a few remarks to the society 
on the subject of immersion objectives, with particular reference to the increase 
of aperture which the immersion system developed over the maximum apertures 
of dry objectives. The remarks he had then made appeared to have produced 
an impression on the Hon. Secretary of the society, and at the conclusion of the 
meeting that Hon Sec., with a zeal peculiar to the energetic race of honorary 
secretaries, pressed him to promise a more detailed exposition of his views on 
aperture and matters relating thereto. In fulfilment of the promise then extracted 
from him, Mr. Mayall said he had come to Liverpool, not however with a formal 
paper on the subject, but with the intention of giving a few illustrations in 
popular form, which might fittingly be given under the heading of ‘‘ Brass and 
Glass.” By ‘‘ Brass and Glass” must be understood that part of microscopy 
concerned with the development of the microscope as an instrument apart from 
its applications to this or that special branch of study. Mr. Mayall said that it 
had recently been most ungenerously stated in public that the “ Brass and 
Glass” party among the microscopists cared for nothing but mere display of 
elaborate apparatus, that they vied with each other in encouraging the manu- 
facture of more and more expensive instruments for the gratification of their 
personal whims and fancies, and without the slightest reference to advancing any 
scientific branch of microscopy. It was no part of his programme to explain in 
detail what really was expected to be gained by encouraging opticians to con- 
struct stands, objectives, condensers, all which from their elaboration must 
necessarily be costly; but might point generally to the fact that the most con- 
spicuous developments in recent microscopy—particularly the delineation of 
microscopic objects by means of micro-photography—were absolutely dependant 
on the perfection of the instrument. Now the improvement of the instrument 
itself was by no means so petty a subject as it had been sought to insinuate. 
He (Mr. Mayall) thought that a thorough investigation of the principles upon 
which the improvement of the instrument depended, was by no means an un- 
worthy or idle task; and he thought that if those principles were more 
generally appreciated, much more rapid strides would be made, and certainly 
there would be far less publicity given to crude and erroneous interpretation. 
The ground would in fact he cleared of much mere controversial verbiage. 
Taking, as an example, the prevalence of erroneous views with regard to the 
meaning and function of aperture—he would endeavour to give to the meeting 
a clear statement of the old theory of this matter, and meet it point for point 
as the newer views of which Professor Abbe, of the University of Jena, was the 
originator. Then by means of a large number of diagrams which he drew on 
the blackboard illustrating his subject, Mr. Mayall dealt at considerable length 
on the main features of what he termed the “Aperture Controversy,” concluding 
his remarks in that branch by an earnest appeal to all present if they had any 
difficulties to suggest to suggest them forthwith—as it was the ardent desire of 
himself and those with whom he was associated in the controversy to have 
every point of difference thoroughly explained, their sole motive being the pro- 
mulgation of accurate views. Mr. Mayall also exhibited and described in 
