1875.1 Physics. 121 
Marine Fossil and Sub-Plutonic Deposits, being stony and possessed of 
very much the same physical characters, are manipulated in the same manner. 
A small lump of the deposit is placed in a test-tube, and covered with a strong 
solution of caustic potash. Itis then boiled for a few minutes, and usually it 
immediately begins to break up and fall down in the shape of a soft mud-like 
material. At once the liquid, with the suspended fine powder, is poured off 
‘into a large quantity of clean hot water, and if the whole of the lump has not 
broken down into a powder, what remains has a little water poured over it in 
the test-tube, and is again boiled. It will be found that a little more will now 
crumble off. This is to be added to the rest in the large vessel, and if the lump 
has not now broken down, it is again boiled in the alkaline solution and in 
water alternately, until it has all been disintegrated. It is then all permitted 
to settle for at least three hours, when it is thoroughly washed and boiled in 
hydrochloric acid for about half-an-hour. There is then added an equal 
amount of nitric acid, and the boiling continued for a short time. It is then 
washed and heated in sulphuric acid with the addition of bichromate of 
potash and hydrochloric acid. 
The following preservative fluid is recommended for mounting recent speci- 
mens. To one ounce of distilled water add two or three drops of wood 
creosote and a sufficient quantity of alcohol to make the creosote soluble in 
the water; this will about equal double the quantity of the creosote. The 
methods of mounting recommended by Dr. Edwards are those well known to 
all skilled microscopists. 
In a paper on blue and violet stainings for vegetable tissues, Dr. C. Johnson, 
of Baltimore, gives the following formule fora useful stain for this purpose :— 
Ordinary logwood extract is finely pulverised in a mortar, and about three 
times its bulk of alum (in powder) added; the two invredients are well rubbed 
up together, and mixed with a small quantity of distilled water. The complete 
admixture of the alum and haematoxylin is necessary, and this will require fifteen 
or twenty minutes vigorous trituration. More water may now be poured on, 
and the solution, after filtration, should present a clear, somewhat dark violet 
colour. If a dirty red be obtained more alum must be incorporated and the 
mixture again filtered. After standing several days add 75 per cent alcohol 
in the proportion of two drachms to one ounce of the fluid. Should a scum 
form on the surface of the liquid at any time, a few drops of alcohol and care- 
ful filtering will be all that is required. This fluid colours very rapidly, 
requiring but a few minutes, whereas, if a slower tinting be desired, the fluid 
may be diluted with a mixture of one part alcohol and three parts water. 
The sections to be stained having been kept in alcohol, place them in a 
weak dilution of the fluid and watching the result, transfer the morsel to dilute 
alcohol for washing, and afterwards to strong alcohol in anticipation of 
mounting. If it be intended to display the general structure let the tint be 
decided; but if it be wished to give prominence to the vessels a faint blue 
only should suggest the other parts. In treating thin leaves or fresh green 
sections, the colour must first be removed or else staining will be of little ser- 
vice. The bleaching is to be accomplished through the agency of Labarraques’s 
solution of chlorinated soda, in which the objects should be macerated until 
perfectly colourless and transparent. They should then be immediately trans- 
ferred to distilled water for an hour or two, and then to a 3 per cent solution 
of oxalic acid in 50 per cent alcohol, which neutralises the soda and prepares 
the tissue to take the dye, particularly if aniline blue is employed. The oil of 
cloves process is to be employed in the final mountingin balsam. The aniline 
solution preferred by Dr. Johnston, is ‘‘ Bower’s Blue Ink” slightly acidulated 
with oxalic acid, Dale’s soluble blue No. 3 (Robert Dale and Co., Hulme, Man- 
chester) is also recommended. Staining with aniline blue is somewhat more 
uncertain than that with the hematoxylin solution, and the colour of the latter 
‘is preferable, especially for observations by artificial light. 
The antennz of the male gnat, Culex pipio, have long been favourite obje‘ts 
with microscopists, and when viewed under the binocular and suitably illu- 
minated are scarcely surpassed by any low power object. Some experiments 
on an allied species, Culex musquito, by Alfred M. Mayer, go very far to prove 
VOL. V. (N.S.) Q 
