Ernst Leitz

“ The apochromatics as a matter of fact do resolve the fine markings of test objects (butterfly scales and diatomes) somewhat more clearly than the achromatics, but the difference is slight and in ordinary stained microscope preparations is hardly detectable.
The correction of both achromatics and apochromatics is complete. The ordinary Huyghenian eye-pieces are consequently well adapted for use with the objectives of either construction. Only with the highest powers is it desirable to make use of the so-called "compensation" eye-pieces. ”

“ The Oil-immersion, represented by the last illustration consists of a front lens, hemispherical, behind which is a meniscus, which is in turn followed by a doublet and a triplet, these latter acting as the correcting lenses of the combination.
We manufacture both Achromatic and Apochromatic objectives. They differ in that the glasses made use of in the apochromatics and the manner in which they are combined permit a more perfect correction of chromatic aberration. This advantage is not gained without a certain sacrifice of simplicity in construction ”

“ Both the body tube and graduated draw tube are very wide and permit the use of low power objectives to cover specimen of large extent; for the same reason the opening in the stage is very wide but can be narrowed down by a stop.
The most important innovation on the microscope is the new fine adjustment device, which is unexcelled both in solidity of construction and accuracy of movement, representing the highest attainment of the designers and mechanics skill. ”

“ They make excellent laboratory stands for elementary courses in microscopy.
In Stands IV and V the coarse adjustment is by means of sliding tube. They are all provided with fine adjustment by micrometer screw.
Stand VI is provided with rack and pinion adjustment only. It has a large stage, and is particularly intended for searching for trichinae and for similar examinations where a very strong durable stand is desired and where the use of high power objectives is unnecessary. It may also be useful as an auxiliary stand for purposes of demonstration in laboratories. ”

“ The precise mathematical calculation, combined with accurate systematical working and testing methods, make it possible for us to guarantee our objectives to be all of equal and excellent quality.
Every objective before leaving our hands, is subjected to the most careful test, and only such lenses as are of the highest grade, are sent out. ”

“ In the manufacture of our objectives only such glass is employed as has been subjected to the most rigid scientific tests. By these the exact index of refraction and the exact degree of dispersion of the glass are determined, and with these data available it is possible to very perfectly correct both spherical and chromatic aberrations while still making use of wide angular apertures in the objectives. ”

“ This principle has been applied to our machinery as well as to our workmen, with the result that we have gradually accumulated a large plant of special machinery of the most accurate construction, each machine especially adapted to the manufacture of some particular part of our microscopes. By this development of mechanical appliances for microscope manufacture two ends have been attained:—The greatest accuracy and uniformity of construction of our microscopes has been made possible, while at the same time it has been possible to cheapen the cost of manufacture. ”

“ Large Projection Apparatus.
In this projection apparatus an electric projection lamp is made use of, the lamp being available for electric currents of 20 Ampères and about 48 Volts. To regulate the current a rheostat is necessary. When using constant current the carbons should stand at an angle in order to utilize to best advantage the stronger light of the positive (upper) carbon. For spectroscopic projections the carbons of the lamp have to be in vertical position.
Connected with the lamp is a triple condenser of 150 mm aperture. ”

“ The slide carrier has a stop at both ends which facilitates its adjustment in the axis of the instrument, and is arranged for the simultaneous reception of two slides, so that while one is being projected it may be charged with a second which may then without delay be pushed into the optical axis as the first is removed. In this way series of pictures may be thrown on the screen without interruption.
When so arranged the projection can be made upon a screen 30 feet from the apparatus, over the heads of an audience.
Prices:
(The same, adjustable $45.—.) ”

“ Iris diaphragm fitted to stage of stand III.
Stand III can be had with iris diaphragm fitted in stage, in place of the wheel diaphragm (see page 43) Additional price
$6.—
Complete Microscope Outfits.
The outfits comprised in the following pages are made up with achromatic objectives, which suffice for all ordinary needs.
We are glad to supply any other combination of eye-pieces and objectives which may be preferred. The price of each outfit may be readily computed by adding together the cost of its various items.
Microscope stands, without objectives, will not be sold separately. ”

“ If we let u represent one half the angular aperture of an objective, represented in the diagram by D'BN in the case of the immersion, and n the index of refraction of the medium interposed between the cover-glass and the objective we have in the formula n sin. ”

“ The microscope condensers and diaphragm holder. A larger tube fits over the tube of the bellows and carries on a revolving arm the cylinder diaphragm and the two condensers. For low power objectives Nos. 1-3, the cylinder diaphragm and the condenser of longer focus have to be used. The latter at the same time serves as the objective for lantern slide projection. [88]
The other condenser is especially needed when high powers are employed (Objectives 4 to 6) . A small rack and pinion arrangement serves for the adjustment of condenser and diaphragm. ”

“ This micrometer fine adjustment is exceedingly accurate and reliable, and besides it has the following advantages;
By virtue of its unique construction the movement is continuous, there is absolutely no limit to the motion of the micrometer screw, which may be turned forward or backward as the work requires. ”

“ Stand III is now provided with rack and pinion coarse adjustment instead of sliding tube. In consequence a nose-piece can be used on it to better advantage. It will be found an excellent laboratory stand at low price. ”

“ The sub-stage, with condenser, iris diaphragm and mirror,
4. The body with the adjustments,
5. The tube, carrying eye-piece, nose-piece and objectives.
1. The foot and upright support are solid and are of such weight and shape as to permit inclination of the body of the microscope to a horizontal position. The foot is horse-shoe shaped and is made to touch the table at three points, thus insuring stability even on a surface which is not entirely level. ”

“ Stand II with round centering stage.
4. Stand IV is replaced by a model of larger size.
5. Photo-micrographic apparatus for use in horizontal and vertical position, having joint for inclination, large size bellows and plateholder.
6. Large projection-apparatus for electric lamp of 30 Ampère with triple collecting lens of 210 mm aperture.
7. Objective 1 a with adjustable mounting and changeable magnification. It is an excellent objective of low power for general purposes, having a comparatively short working distance. ”

“ These cases are furnished with the microscopes without extra charge, when a complete outfit, including oculars and objectives is purchased.
Object clamps and test objects accompany every microscope.
The objectives to Stands A, I, Ia, Ib, II, IIa, IIb are in brass boxes; those for Stands III, IV, V and VI are in morocco cases.
[20]
Illuminating Apparatus. a. Illuminating Apparatus of Stands A and I.
The apparatus includes the following parts:
Cylinder iris diaphragm. ”