The President's Address. 
33 
objective^ and to take a picture in eacli state. By this, method 
he succeeded in getting pairs^ which, combined^ gave good 
stereoscopic effects. 
5. The second of these papers, ^''On the Photographic 
Delineation of Microscopic Objects/^ by E. L. Maddox, M.D., 
was communicated by ^r. Shadbolt. (Eead November 12th; 
published 'Trans. Mic. Soc./ vol xi, N. S., p. 9.) 
The author, admitting the difficulties attending the attempt 
to produce well-defined and useful representations of objects 
as seen through the microscope, and that pictures so obtained 
can at best only give a general view of an object or of some 
particular part, still regards the process as advantageous, 
because in the pictures there can be " no notable mistakes of 
relative magnitude, distance, or separation of parts, upon the 
strict correctness of which much in scientific observation 
depends ; also parts incapable of being easily, if at all, ren- 
dered by the hand can by its use be traced in more than mere 
outline. Strong sunlight, if possible, is used on all oc- 
casions, though this is attended with the risk of softening 
the cementing medium of the lenses of the object-glass. In 
the discussion which followed the reading of the paper, the 
Rev. J. B. Reade remarked, that the injury of the object- 
glass might be avoided by the dispersion of the heat rays, 
which could be effected by an arrangement he had long ago 
used for that purpose ; and Mr Highley suggested that the 
heat rays could be intercepted if the illuminating pencil 
were made to pass through a solution of alum. 
6. A paper '^'^ On the Scales of some Species of thysa- 
noura," by Mr. Richard Beck, was read March 12 ; pub. in 
'Trans. Mic. Soc.,' vol x, N. S., p. 83. 
The author considers the scales of some of these insects 
as test objects of great value, as affording the means 
of determining the exact condition of a combination as to 
the centring of its component lenses, and its corrections for 
aberration and dispersion. The proper scales (known gene- 
rally as Podura scales) are really obtained from a species of 
Lepidocyrtus ; but the precise species is not yet certainly de- 
termined. The author mentions the difficulty of finding the 
insects, gives the results of his experience in searching for 
them, adds instructions for capturing them when their 
haunts are ascertained, and for transferring their scales to 
the glass which thenceforth is to bear them. He tells us 
there is danger of the insects hopping away and effecting their 
escape before the transfer is completed, but assures us this 
may be secured by a moderate dose of chloroform, which he 
administers by dropping a little near them upon the paper 
