216 NOTES AND MEMORANDA. 
various papers on zoology, communicated from time to time to the 
different associations, the great work by which his name will be 
remembered is the ‘ Monograph of the British Spongiadex, a book 
published in 1864 by the Ray Society, and which has been admirably 
illustrated by Mr. Lens Aldous. 
Mr. Bridgman’s Mode of Polishing a Speculum. — In a paper 
published in the February number of the ‘Quekett Club, Mr. Bridg- 
man gave an interesting account of a new universal reflecting illu- 
minator, which we regret that we cannot condense, as without the 
illustrations our remarks would be unintelligible. However, he also 
appended some observations on the above subject which are worthy of 
being recorded here. He says :—Having obtained the silver plate, 
and had it soft-soldered to a brass back and cut to the size, let a piece 
of sealing-wax or a small block of thick plate glass be attached to its 
back as a handle and to prevent flexure. Now procure a common 
writing-slate with a flat and smooth surface, and grind the silver with 
water until all scratches have disappeared, and a level face has been 
produced. If the surface be now well burnished with a straight 
burnisher it will add greatly to the brilliancy and durability of the 
polish. Next, take two pieces of thick plate glass, not less than three 
or four inches square, and upon the surface of one melt some pieces of 
clean pitch until soft enough to be spread evenly with a hot knife to 
about the thickness of a sixpence. Let the surface of the other glass 
be smeared with soap and water, and then pressed upon the soft pitch 
until the latter shall have acquired a flat and highly polished surface, 
when it may be slid off, and the pitch left to harden. Obtain at the 
chemist’s a pennyworth of “ precipitated carbonate of iron” (the softest 
and finest “rouge” possible), and mix with a few drops of water to the 
consistence of cream, and let the metal be lightly worked with this 
over all parts of the pitch in small circles, carefully avoiding all dirt 
or grit until the polish, commencing in the centre, shall have spread 
to the edges, and have a deep and brilliant lustre that will reflect 
objects with the utmost sharpness of definition. 
A New Microtome for cutting a series of sections was recently 
described to the Boston Society of Natural History, by Mr. C. 8. 
Minot. We have not yet seen any description of the instrument. 
Mr. Spencer’s Objective.—In our last number we described an 
objective of Mr. Charles A. Spencer, on the authority of the ‘Cin- 
cinnati Medical Journal.’ We now learn from that Journal that 
the object-glass referred to was not made by the veteran Spencer, 
but by his son, who, it states, with his father, and brother-in-law, 
O. T. May, is engaged in the manufacture of microscopes, under the 
“firm name” of Charles A. Spencer and Sons, in connection with the 
Geneva Optical Company. The immediate work of making these 
fine lenses is done by Mr. Herbert R. Spencer. The glass alluded to 
is a three-system lens, and is of 170° angle of aperture, instead of 
160° as stated. 
