122 Progress in Science. [January, 
that the beautiful whorls of fibres with which the antennz are armed serve the 
purpose of very delicate auditory organs. Observations under the microscope 
upon living mosquitos show that the delicate sete respond to the vibrations of 
tuning-forks, some vibrating to certain notes while the others remain at rest. 
Further experiments would seem to determine the function of this singular 
auditory apparatus, namely, to guide the male in the direction of the peculiar 
humming made by the female. The paper is too long for the quotation in full. 
Mr. J. K. Jackson communicates to ‘‘ Science Gossip” a process for fixing 
diatoms in devices. The operator is supposed to start with a stock of perfe@ly 
clean material, and that a ‘‘dip’’ has been evaporated ona slide. The tool 
used isa hair from a cow’s neck, mounted in a light wooden handle.* The 
diatom selected is picked with the hair under a 14-inch power and 
placed on a prepared thin cover, made as follows:—Take filtered gum traga- 
canth, and mix five or six drops with one ounce of distilled water. The covers 
are then cleaned and placed on a rack formed of six pieces of wood, six inches 
long, a quarter of an inch broad, and one-eighth of an inch thick, made into a 
‘“‘rack”’? by having pieces of copper wire run through the lot near to each end, 
so that the bars of the rack slid on the wires may be altered to suit different 
sizes of covers. Each cover has then a minute drop of the gum placed on its 
centre with a fine pipette, special precautions being taken to prevent the intro- 
duétion of dirt. The loaded rack is then transferred to the hot plate and the 
gum dried as speedily as possible. The covers when dry are stored for use 
under a well closed glass shade. When required for use, one of the covers is 
placed on a wooden slide having a hole suitable to the size of the thin giass 
employed. On this cover the diatoms selected are placed with the cow’s hair. 
When sufficient frustules have been collected to form the device, they are 
‘‘ pushed, coaxed, or driven,” into the required form, under an inch and a half 
objective. When this has been accomplished, after the exercise of much 
trouble, patience, and dexterity, the cover with its device must be brought close 
to (just within) the mouth, and breathed upon—one slow, long breath. The 
cover must then be dried upon a hot plate and turned over on to a drop of 
balsam and benzol, or damar, in the centre of a slide, and if the glaze on the 
cover be of the proper thickness, the balsam may be boiled without displacing 
asingle diatom. The writer adds the following hints:—(1). Never hope for 
one drop of clean water unless you distil it yourself. (2). Place your diatoms 
**on their backs” in the gum, else they will retain air, which nothing can 
expel. (3). ‘‘ Mind your eye,” or rather your eyes, as the process is a very 
trying one to the sight. 
Mr. G. J. Burch has communicated to the Quekett Microscopical Club his 
method of making extremely thin glass covers. Take a piece of glass tube about 
a quarter of an inch bore, seal up the end with the blowpipe, and continue the 
heat until the glass is so soft that it will fall out of shape, unless you keep 
turning it round; removeit from the flame, and blow into it with all your strength. 
It will be seen to swell, at first slowly and then suddenly, to a large bubble of 
very thin glass. Supposing the tube to have been sealed up with as little glass 
as possible, it may be blown out to about four inches diameter. When cold 
break it up and cut the pieces to shape with a writing diamond. The glass is 
of course curved, but it may be flattened by being placed on a perfectly flat 
piece of platinum foil, and depressed for a moment into the Bunsen flame; as 
soon as it is red hot, it will sink down to the flat foil. This has also the effe& 
of annealing it. A piece of this glass was found upon measurement with the 
micrometer to be only o0'0004 of an inch. 
Heat.—Dr. G. Krebs, in a paper on the determination of the freezing-point 
for delicate thermometers, says :—Schultz, in his treatise on the freezing-point 
of the water of gaseous solutions and the regelation of ice, shows that the 
freezing-point of water is lowered by dissolving gases, the change being nearly 
proportional to the amount of gas dissolved. That water holding solids in 
solution freezes at a lower point is well known. Thomson and Clausius have 
shown from the principles of mechanical theory of heat that the freezing-point 
* A fine bristle split at the end is preferred by some authorities. 
