“Sir,
“Accept our thanks for your extreme complaisance in offering to publish the results obtained by us in the construction of microscopes. Since the order executed for Mr. Lister, we have improved those instruments last completed, by greatly enlarging the diameter of the illuminating mirror, in order to obtain still greater light. The prism for opaque bodies is diminished about one half, and by a small modification in its mounting is rendered more serviceable: the diminution of the length of the body has enabled us to augment the magnifying powers by different eye-glasses, and the four double object-glasses placed in a better mounting can be used separately or in superposition, according to the pleasure of the observer, either to form quadruple objectives, or even to combine in a mass together. This last arrangement produces a great accession of magnifying power, without injuring the clearness of the image or arresting much light.
“You see, Sir, that we have the pleasure of coinciding perfectly in your opinions about improvements, for we adopt the quadruple object-glass as the best, and we give three changes [p256] of eye-pieces. The double motion given to the body of a microscope is, in our idea, the defect of all those hitherto constructed; for, as the optical part should remain perfectly centred with the mirror and the diaphragms, it is evident that the least derangement of it from this position must destroy the perfection of the image: the stage then only should move[47] without affecting the diaphragms or the mirror, and in this we [p257] have well succeeded in the construction of the microscope of Sig. Amici. But all these arrangements much augment the price, and an observer ever so little practised will always find the object easily enough by means of his hands.
“The prices of our achromatic microscopes are as follows:—
“Achromatic microscope, like Mr. Lister’s—300 francs.
“The same, with the latest improvements, three eye-pieces, and camera lucida for drawing the magnified objects—400 francs.
“Amician Microscope, one horizontal achromatic, the stage giving all the motions to the object, with a micrometer screw, five eye-pieces, two camera lucidas, hand magnifier, frog trough, accessary apparatus, &c. One catadioptric microscope, mounted on the same stand, and adapting itself to the same apparatus; the two instruments inclosed in a mahogany case—1000 francs.
“We trust that the very moderate prices of these instruments, together with the care which we bestow on their construction, will procure us orders for them. Their superiority has been duly recognized by the jury of the Exhibition of the Products of Industry, which has been pleased to decree to us a silver medal.
“The Amician achromatic microscope is composed of a tube seven inches long, at the extremity of which is placed a prism, which reflects at a right angle the rays which come from the object-glass, composed (as in our microscopes executed since 1824) of four double object-glasses, which may be used separately, or two, three, or four at a time. The stand is a square bar, which has a rackwork, carrying a moveable stage, which, by means of adjusting screws ingeniously disposed, permits an object to traverse the field of view in every direction. This disposition gives the power of determining the real dimensions of objects submitted to observation by means of the micrometer screw, which is placed at the side, while the camera lucida affords the means of drawing their outline, and consequently of measuring the magnifying power.
“The rays proceeding from the object which have passed the object-glass, and have been rendered horizontal by the prism, are received by different eye-pieces disposed after the manner of [p258] Ramsden. Their power can be varied. Each instrument carries six, five of which can be attached at pleasure either to the catadioptric or the achromatic. The deepest belonging to the reflector is a single lens of half a French line focus, and the most powerful of the achromatic is a line and a half.