98 
Transactions of the 
The past year has been marked by decided improvements in the 
construction of object-glasses. A remarkably fine |th has been 
made by Messrs. Powell and Lealand, with an avowed single front 
lens ; but how far its principle of construction may agree with, or 
differ from, that previously enunciated by Mr. Wenham, cannot 
at present be stated, as its construction has not been made public. 
The image formed by this lens bears amplification by very deep 
eye-pieces exceedingly w T ell — than which there can be no more 
certain a test of first-rate definition. 
In the object-glasses constructed on Mr. Wenham’s formula 
considerably increased flatness of field has been obtained by substi- 
uting two plano-convex lenses of proportionally less curvature for 
the single plano-convex posterior lens originally employed. The 
writer has in his possession a |th on the improved model, and can 
without hesitation affirm that it is superior in definition, and far 
superior in clearness and absence of fog or milkiness, to any other 
objective he possesses — these comprising a |th and |th by Andrew 
Eoss, a jfth and iVth by Thomas Boss, and a I 1 e th and ^th by Powell 
and Lealand ; all considered first-rate by their respective makers. 
The definition of this lens can by no means be broken down by the 
sixth eye-piece of Boss, a much deeper ocular power than the 
writer would ever think of employing except as a test of definition. 
As regards fog, this defect is very conspicuous in the -gth by 
A. Boss. The construction of this object-glass is a single front 
lens followed by three cemented combinations. There are some 
reasons for surmising that fog is partly due to the multiplication 
of cemented contact surfaces ; and if this be so, the general princi- 
ples of analysis would lead to the conclusion that the amount of 
the defect in question would be in proportion to the square of the 
number of cemented surfaces, rather than in the simple ratio of 
that number. Thus this |th, which has four cemented surfaces, 
might be expected to present four times as much fog from that 
cause as the jth above mentioned, which has only two : this is 
thrown out rather as a suggestion for observation than as an 
assertion of a fact. 
Your President cannot but regret that in the past year some 
intemperately conducted correspondence should have appeared in 
the pages of the ‘ Monthly Microscopical Journal.’ This fact has 
much strengthened a conviction, long entertained, that whenever 
this Society may have the good fortune to find itself in a better 
financial position than that existing at the present time, it will 
greatly redound to its credit and prestige to follow the example 
of the older Boyal Societies and publish its own Transactions, 
unmixed with extraneous matter, however valuable, or however 
cognate to the objects and pursuits of the Society. 
The Society may be congratulated on the valuable contributions 
