ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 
535 
of his eye-piece, with the view of reducing the spherical aberration. By 
mounting the objective fronts in a wheel instead of in a slide, Martin 
effected a great improvement, and so became the inventor of that useful 
appendage, the rotating nose-piece. 
Now, as these early Microscopes were largely used as simple Micro- 
scopes, a long extension of rackwork would be necessary, which, judging 
from the cut, the Compendious Pocket Microscope certainly did not pos- 
sess, and it is more than probable that the draw-piece added by Martin 
was for the purpose of -remedying this very defect. 
The improvements effected by Martin in substage and superstage 
illumination were of course a distinct advance. 
In conclusion, Adams’ Compendious Pocket Microscope is important 
because it undoubtedly led up to Martin’s model of 1776, which was 
one of the best and most practical of old non-achromatic Microscopes, 
and of which, thanks to Dr. Dallinger, we have such a fine example in 
our Cabinet. 
Fine Adjustment of the Microscope.* — A treatment, mainly his- 
torical, of this subject appears over the signature “ M.” At the com- 
mencement of this century, micrometer movement w r as confined to the 
stage ; for the last forty or fifty years it has been applied to the upper part 
of the stand. Such stands, closely resembling those in present use, were 
already constructed in 1839 by Charles Chevalier, and improved by his 
son Arthur Chevalier. Strauss’ “ Grand Microscope ” possessed coarse 
and fine adjustment, rotatory object-stage, and a movable slide in each 
direction, besides apparatus for central and oblique illumination, a re- 
flecting mirror for incident light, a camera lucida, an objective stage 
micrometer, and an eye-piece micrometer. The tube was mounted on 
a horseshoe foot, and arranged for oblique inclinations. The well-known 
Parisian opticians, Trecourt, Bouquet, and Oberhauser, worked to this 
model, and in 1857 the latter entered into partnership with his nephew, 
E. Hartnack, who since 1860 has conducted the business alone. Ober- 
hauser and Hartnack then for a long time controlled Microscopy, 
because they produced a combination of the best mechanical execution 
and optical design. By means of his immersion system of 1860, No. 10 
with 1*6 mm. focus, and No. 11 of the year 1864 with 1*2 mm. focus, 
Hartnack surpassed all known objectives (even the English), which 
possessed even a smaller focus but a much smaller interval ( Abstand ), 
and were therefore not so well adapted for practical use. 
The first large system, No. 11, was produced by Hartnack for Prof. 
Henry von Heurck in Antwerp, who has published a very favourable 
report upon it in the first volume of the ‘ Annales de la Societe Physio- 
logique d’ Anvers.’ 
By means of these stands the original micrometer movement of the 
stage was quite superseded ; all better instruments were provided with 
a fine adjustment, which was placed in the arm of the tube-holder. 
Only cheap stands now show a fine adjustment by oblique movement 
of the object-stage ; obviously this cannot be applied to stronger systems, 
because the object must lie nearer to the upper lens aperture than to the 
lower, and consequently cannot be symmetrically adjusted. 
* Zeitschr. f. angew. Mikr., July 1898, pp. 86-90. 
