58 General Notes. [January, 
tine, oil of cloves and the like; these, however, give very unsatis- 
factory results. My friend, Dr. C. B. Johnson, of Providence, 
R. I., informs me that he has sections of wood which have been 
laying in oil of cloves for over three years, and from which the 
bubbles of air have not been at all removed. Perhaps the same 
may be said of the oleo-resins. Recourse has also been had to the 
air-pump; the idea being that an object placed beneath the bell 
glass, a few strokes of the piston will suck out all the air from it. 
But although in theory this seems plausible enough, yet as a per- 
fect vacuum cannot be attained, some air, be it ever so small 
an amount, must render the objects of no use for microscopic 
examinations. 
Thus have microscopists been at their wits’ end to discover 
some process by which their object can be perfectly and satisfac- 
torily accomplished. As no notice has been made of late of any 
new procedure in this direction, I think my friend, Dr. Johnson, 
who has had great success in mounting objects for. the micro- 
scope, can justly be entitled to the first discovery of a mode for 
the removal of air, at once simple and effective. The apparatus 
he employs is of very simple construction, being a digester, or, as 
in his case, a common dentists’ vulcanizer, the means—steam. 
The specimens to be thus treated, especially those of wood, are 
prepared in the usual way, and made ready for mounting. They 
are next placed in a small vessel of any material which will resist 
a certain amount of heat. Dr. Johnson uses a small glass phial 
in his experiments ; this is filled up with water after all the speci- 
mens, as many as it can conveniently hold, are placed within. A 
` cork can be used, but a slit must be cut in it to allow the escape 
of air and the admission of steam and hot water. A little water 
is now poured into the vulcanizer, the bottle of objects placed 
within and the lid of the machine screwed air tight. The whole 
is now heated to a temperature of about 300° Fahr. for a few 
minutes. This temperature is sufficient for all practical purposes; 
a higher degree of heat is unnecessary, or a longer time to 
remain at the given temperature needless. 
When sufficiently cooled the phial is removed, the water 
drained from the bottle and alcohol substituted. The specimens 
are now ready for mounting, or can be bottled and set away 
indefinitely for use. 
This constitutes the whole process; by it the specimens are 
absolutely free from air. Perfect satisfaction is guaranteed ; and 
in every case we are absolutely sure of the results, provided of 
course that the proper care has been taken. 
The modus operandi seems to be that the steam penetrates the 
pores of the wood or other substances, and forces out the air whose 
place it takes. The air is then absorbed by or dissolved in the sur- 
rounding medium. The woody fibres are not destroyed by the hot 
and compressed steam, except the soft tissues, as one would at first 
