en seldom content themselves with an instrument under one form; hence such a variety of microscopes, hence many alterations in the Lucernal Microscope. Mr Adams himself, we understand, has fitted up this last in a great many different ways; and it is reasonable to think that no person is more likely to give it every improvement of which it is susceptible. Of the alterations by other hands we shall only particularize one, made by Mr Jones of Holborn (B), whose description is as follows:

A represents a portion of the top of the mahogany box. Microscope box in which it packs, to preserve it steady; it slides in a dove-tail groove withinside, a similar groove to which is cut in the top of the box A; so that when the instrument is to be used, it is slided out of the box withinside, and then slid into the groove at top ready for use, almost instantly, as shown in the figure. The adjustment of the objects is at the stage B; for the right focal distance is readily and conveniently made by turning the long screw-rod BB, which goes through the two pillars supporting the box, and works in the base of the brass stage E; which base is also dovetailed, so as to have a regular and steady motion in another brass basis that supports it. In this instrument, therefore, the pyramidal box does not move; but the stage part only, which, from its small weight, moves in the most agreeable and steady manner. While observing the image of the object upon the glass through the sight-hole at G, the object may be moved or changed by only turning the rack-work and pinion applied to the stage by means of the handle D, for that purpose. By this contrivance you have no occasion to change your position during the view of the objects upon one of the slides. This motion changes the objects horizontally only; and as they are generally placed exactly in one line, it answers all the purposes for which this motion is intended very well. But it may sometimes happen that the observer would wish to alter the vertical position of the object; to perform which there is another plane rod at F, that acts simply as a lever for this purpose, and moves the sliding part of the stage E vertically either upwards or downwards.

Thus, without altering his position, the observer may investigate all parts of the objects in the most satisfactory manner. Rack-work and pinion might be applied to the stage for the vertical motion also; but as it would materially enhance the expense, it is seldom applied. The brass work at the handle of D contains a Hooke's universal joint.

The brilliancy of the images of the objects shown upon the large lenses at the end of the box, being very frequently so great as to dazzle the eyes, Mr Jones applies a slight tinge of blue, green, and other coloured glasses, to the sight-hole at G, which softens this glare, and casts an agreeable hue upon the objects.