ON THE SO-CALLED VESICULAR VAPOURS OF WATER, ETC. 
27 
their flattened surfaces they possess but little power to deviate the light from its 
regular course. Their shape is very irregular, generally of an angular, and frequently 
of an hexagonal form. See fig. 1. aa. That part condensed on the surface of the 
balsam presents exceedingly minute globules of the same nature. 
Instead of condensing the breath as above, I have placed the slip of glass covered 
with balsam in the open air, on grass covered with hoar-frost, and after it had become 
slightly turbid on its surface from the moisture deposited, I submitted it to the 
microscope. It was then seen to be covered with lines of single globules like strung 
beads, following the most tortuous courses ; and wherever the balsam had been dis- 
turbed by the passage of any body through it even for a long time previous to the 
exposure, the direction of these lines showed the manner in which it had been dis- 
turbed. The diameters of some of these globules appeared as mere points under the 
strongest magnifying power, and were probably less than 0 , 0001 mm . As the glass 
became warm the globules coalesced at intermediate points into a single one, which 
soon vanished in its turn. When steam from boiling water in a glass tube was 
condensed in Canada balsam, the globules which are represented in fig. 2 are much 
more voluminous, varying from 0'01 min to O'Olfi 111111 , though in other respects they were 
exactly the same. The globules arising from water at 60° Reaumur are the same 
size as those of the breath. 
No doubt can possibly be entertained, after having inspected these globules atten- 
tively, of their being perfect spherules of liquid without any central part whatever, 
for containing a gasiform fluid, which could not escape detection when they coalesce 
and adhere to the glass. Globules of gas, of whatever nature, cannot possibly be 
confounded with one of these liquid globules, from their being much darker, and 
the smallest of them considerably larger than those of water, independently of their 
remaining permanent when inclosed between two surfaces of glass. In Canada 
balsam they present, on a very minute scale, the exact representation of external 
objects which surround the microscope, which, however, is seen on liquid globules 
when they are sufficiently large. Thus, in looking through the microscope, I have 
seen at the lower part of one of these air-globules portions of my own face or body; 
and in the same way an extensive view of trees, houses, &c. may be traced with all 
its details on one of these microscopic globules not larger than 0 - 01 mra or 0 - 02 mm . 
Fig. 3 represents the image of part of the hand, as seen in a globule of air, drawn 
under the camera lucida. I mention this fact, as I believe that the telescopic action 
of the microscope, by means of these hollow prisms, may be capable of several 
interesting applications. 
By breathing gently on the surface of Canada balsam, it will become covered with 
a film of moisture, reflecting various colours in proportion to the quantity deposited. 
Any bright object viewed through it will appear surrounded by a halo of brilliant 
colours, such as those seen sometimes encircling the sun or moon. These coloured 
films, under the microscope, are decomposed into colourless particles of water, which 
