270 Progress in Science. [April, 
of from ro to 50 diameters, and requiring a working distance between the stage 
and the binocular prism of 4} to 5 inches, which is quite practicable with large 
stands. Where sufficient working distance cannot be obtained, the object may be 
placed upon the sub-stage, or more conveniently, the sub-stage removed, 
and the body racked down, so as to focus through the empty stage upon 
the table, where the object may be supported by any convenient method. 
A modification of the above has been arranged by Mr. F. Oxley, of the 
Quekett Microscopical Club. Into the nose-piece of the microscope he 
screws a 3-inch or 4-inch objective, and has a sliding fitting made with the 
universal screw to carry an objective placed beneath the stage. The object to 
be viewed is placed on the table, where it can be very conveniently manipu- 
lated; a 13-inch objeGive beneath the stage answers very well in combina- 
tion with a 4-inch (the single combination of Ross) on the microscope. 
This arrangement has the advantage of being inexpensive; it can be 
adapted to any microscope at a cost of a few shillings. This erector is 
free from many of the objections to the usual erec&tor placed within the 
body. The view given of the object is extremely good, and considerable 
variation of magnifying power may be obtained by altering the distance 
between the two objectives. The microscope is really converted into a 
telescope of short focus, the inverted image being formed by the combination 
below the stage, and again inverted and consequently erected by being 
viewed with the binocular microscope. The contrivance is especially valuable 
to those who have dissections or other manipulations to condué& under 
the microscope: all such operations can be carried on in the most comfortable 
manner, with the hands resting on the table, and the body free from the con- 
strained stooping position involved in the use of single microscopes; and 
all these advantages combined with the large field, fine definition, and capa- 
bility of distinguishing vertical distances which are so peculiarly the properties 
of a good binocular instrument. 
“ Silliman’s Journal” contains an account of a new eye-piece micrometer 
and goniometer, designed by Dr. H. T. Porter and Mr. J. P. Southworth. 
The scales in both instruments are made by photography instead of the usual 
process of engraving with a ruling machine and diamond. The original scale 
being drawn upon paper and consisting of 100 heavy black lines about jth 
of an inch apart, the lines marking every ten divisions are 6 inches long, and 
extend 1 inch on each side of the scale; those marking each five divisions are 
5 inches long and extend half an inch on each side; the remaining lines are 
4 inches long. A negative is taken in which the scale is reduced to 2 inches 
in length. From this a transparent positive is taken reducing the scale to 
about half an inch in length. In this the lines are ,3,th of an inch apart. A 
thin glass cover is cemented on with Canada balsam for the protection of 
the lines; it is then mounted in a similar manner to Jackson’s micrometer. 
For the goniometer, a circle about 18 inches in diameter is drawn with 
India ink, and divided into degrees. The centre is indicated by a dot, and one 
diameter is drawn. Every five and ten degrees are indicated by longer lines 
than those indicating single degrees ; every ten degrees of each quadrant are 
numbered from 0° to go’. A negative of this diagram is taken as before, and a 
reduced positive of a size to fit the tube of the microscope; this disc 
is mounted to fit the tube at the focal point of a positive eye-piece. A cobweb 
is drawn across the diameter of the lower lens. When a crystal is to be 
measured, the stage is moved until the apex of the angle coincides with the 
centre of the goniometer, and the diameter with one side. The eye-piece is 
now turned till the cobweb crossing the diameter at the centre coincides with 
the other side of the angle. The number of degrees can be read off at 
the circumference without the trouble of looking outside as in ordinary con- 
trivances or reading the verniers of a rotating stage. The inventors claim for 
these photographic scales the advantages of cheapness and greater legibility 
than that of the usual ruled ones. The transparent spaces are quite clear 
enough not to seriously impair the definition of the instrument. 
In the course of some remarks on the structure of the Arborescent Lycopo- 
diaceze of the Coal Measures, delivered before the Royal Microscopical Society, 
