“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.