94 
HisLOP^ on a New Secondary Stage. 
My task is now completed. The slides which I have sent 
will^ I think^ afford a very good illustration of the Diato- 
maceae of this part of Wales. With one exception, that of 
No. 146_, which was from Tenby, and sent me by my friend Mr. 
Roper ; the whole of the gatherings have been made by 
myself, and I can therefore vouch for their authenticity. 
I trust that the little I have done will prove of interest to 
some of the members of this Society ; at any rate, if it only be 
the means of inciting others to better and more extensive con- 
tributions, I shall feel amply repaid for any trouble I may 
have taken in the matter. 
Description of a New " Secondary Stage." 
By W. HisLOP, Esq. 
(Read June 1 6th, 1858.) 
The want of some simple and effective means of affixing 
the various illuminators beneath the stage of the microscops, 
which shall possess the necessary adjustments for centering 
and focusing, is felt by every one who makes use of the 
instrument for purposes beyond those of mere exhibition. 
Several ^ secondary stages^ have been constructed, which 
have more or less answered the requirements of the case, 
but have also left room for improvement. Most of these 
arrangements have the disadvantage of weight, an element 
of inconvenience in the better class of instruments which it 
is to be hoped has reached its limit. All these various 
methods, too, require the attachment of the various pieces 
from the top or bottom, thus increasing the necessary space 
between the stage and mirror, and risking the derangement 
of the light, which it is often desirable to retain in pre- 
cisely the same conditions. In some instruments the 
adjustments are attached to each piece of apparatus, but 
this immensely increases the quantity of extraneous me- 
chanism. 
The contrivance I have now to submit is one which I 
have had in use for some months, and which I have found 
effective and convenient. It possesses the advantage of 
adaptability to almost every stage ; the illuminators can 
be instantly inserted and removed from the side, and are 
