BY JOHN THOMSON, M.B. 81 
INCH. 
1 inch equals 2.54 centimetres. 
Lae BS 25.4 millimetres. 
diem 3 soe) 2ao micra, p 
Small as the micron is, there are many objects constantly 
under microscopical observation, which are but fractional 
parts of it. And in the calculation of ethereal wave lengths, 
this microscopic micron is again divided into thousand and 
million parts. 
Some of the micrococci are so small that four of them can 
be easily packed into a square micron; most of the bacilli 
are but half a micron broad, while there may be one. two, 
three or more micra long; and some of the stained flagella 
are but fractional parts of a micron or less than the 1-100,000th 
of an inch. 
With few exceptions, the slides exhibited have been 
photographed at a magnification of 1000 diameters—that 1s 
linear—cr 1,000,000 superficial. And this magnification is 
guaranteed, for the microscopical and photographic 
apparatus were adjusted and standardised after careful 
experimenting with stage micrometers. 
In the slides or photo micrographs, the size of any micro- 
organism can be determined at a glance, for a graphic plan has 
been adopted of having a scale, occupying half the picture. 
printed on the transparency along with the micro-organism. 
Each small square of the scale, represents a square 
MICRON. 
Benign, Useful, or Friendly Bacteria.—It is rather 
unfortunate that the public should associate bacteria with 
disease—in fact view them as synonymous terms. 
That we have foes—foes treacherous and implacable— 
amongst these tiny organisms is certain; but we have also 
friends, trusty and reliable, humble, perhaps, and unobtrusive, 
but persistingly working together for our general welfare. 
BACTERIA. 
Their use in the Arts. 
Maceration Industries. 
Linen Hemp 
Jute Cocoa Nut Fibres 
Sponges Leather preparation 
Maceration of skeletons Citric acid 
