Monthly Microscopical I 
Journal, Feb. 1, 1869. J 
PROCEEDINGS OF SOCIETIES. 
139 
Old Change Microscopical Society. 
Charles J. Leap, F.L.S., &g., the President, in the Chair. 
At the monthly meeting of this Society, held Jan. 15th, Major 
Owen, F.L.S., delivered a lecture " On Polycystina," which was illus- 
trated by numerous specimens and drawings. 
Mr. C. T. Kichardson, one of the members, also read a paper " On 
Floscularise." 
The Third Annual Soiree of the Society will be held Feb. 15th, 
at the Terminus Hotel, Cannon Street. 
Natural History Society or Armagh. 
The last meeting of this Society was held on the 13th January, 
Mr. A. J. Mulligan in the chair. Mr. Lewis G. Mills, LL.B., de- 
livered a lecture " On the Manipulation and Preparation of Objects 
for the Microscope." The lecturer stated that of the large number of 
those who possessed microscopes, but few were able to prepare good 
slides, and these persons were chiefly dependent upon professional 
preparers for properly mounted objects. He then showed how that 
such unskilled preparers might turn their microscopes to good account 
by using them in the study of objects which required little manipu- 
lation and no preparation. The lecturer then gave a lengthened 
explanation of usual methods adopted in the preparation of micro- 
scopic objects of different kinds. In speaking of the mode of 
mounting diatoms from fossil deposits, he strongly recommended the 
method of selection as giving the best attainable results from un- 
promising deposits. His observations on the treatment of guano 
were to this effect : — " The guano most readily obtained is the 
common Peruvian guano of commerce ; in this deposit the diatoms 
form a very small percentage of the entire mass, and to prepare the 
deposit for mounting in the rough, according to the usual process, 
would generally give very poor results, and discourage all except 
those well skilled in manipulation. However, the most unproductive 
samples of guano contains some diatoms, and fair slides may be 
prepared from the material, if the process of selection be adopted in 
their preparation. For this process, it is not needful to use more 
nitric acid in the previous cleaning than that which may be necessary 
to clean the diatoms themselves ; and the use of sulphuric acid and 
chlorate of potash is not req^uired, as the bleaching of the unsightly 
foreign material would be useless. A large drop of the prepared 
material must be spread near the edge of a glass slide : the appearance 
of this under a simple microscope with a glass of one-inch focus will 
be that of much dirty material containing a few clean diatoms : the 
best of these latter may be pushed out of the water by means of a 
needle, and nicely arranged near the centre of the slide. The slide 
may now be raised, and the water may be carefully wiped off ; the 
turning of the slide on its edge, or the wiping away of the water will 
not disturb the diatoms selected and placed, as they remain attached 
to the glass sufficiently firmly to admit of the movements required. 
In this way the choice diatoms may be selected out of many drops, 
