The body of the solar microscope is shown at A BCDEF, the part ABCD being conical, and the part CDEF cylindrical. This last part receives the tube G of the opaque object-box. A large concave lens is placed at AB for receiving the rays from the mirror ON P, and converging them into the box HILX.
A brass frame NOP is fixed to the moveable circular plate a b c, and carries a plane mirror for reflecting the sun's light upon the convex glass at AB ; and by means of rackwork moved by the nuts Q and R, this mirror can be turned into such a position with- respect to the inci dent ray, that the reflected ray passes along the axis of the tubes. The microscope is fastened to a window shutter by two screws d, e. The box HILX for opaque objects is shown open. It contains a plane mirror Al for reflecting the light from the lens AB upon the object, and this mirror is adjusted through the door k i to the proper angle by a screw S. Two tubes of brass ale shown at V and K, one sliding within the other, and the outer one V sliding into the box. These tubes carry two magnifying lenses. The interior tube is sometimes taken out, and the exterior one (which is seen within the box) is then used alone.
A brass plate H has its back part fixed to a tube h by means of a spiral wire within the tube, which always presses the plate against the side H of the box. The slid, rs. with the opaque objects shown in Plate CCCLXXViI Fig. 30. pass between this plate and the side of the box, which is done by drawing out the plate II by means of the nut g. The following are the other pat is of the opaque solar microscope.
Fig. 32. is a brass quadrangular slider case, to hold any animal or opaque object, which is to be placed at If, like the other sliders.
Fig. 33. is a four glass slider in a brass frame, for ani malculx &c. which is to be placed between the plates at 7n, Fig 27.
Before using the solar microscope, a circle a little larger than a b c, must be made in the shutter of a win dow opposite to the sun. The mirror NOP is then put through this hole, and the square plate applied to the shutter. The places corresponding to the two holes of the screws d. e, are then marked on the shutter with a pencil, and holes made large enough to admit the screws, which, passing through the shutter, are screwed into their respective holes in the square plate, so as to hold the microscope firmly in its position.
Iti order to use the microscope for opaque objects, the mirror NOP is turned by the screws Q, R, one of which gives it a circular motion, and the other raises or depresses it, till it reflects the sun's rays through the tube upon a white paper screen or cloth, from 4 to 8 feet squat e, placed at a distance of from 5 to 8 feet from the window The tube G of the box HILX is then put into the tube EF, and the mirror Al is adjusted through the door k i till the objects are strongly illu minated. The door k i being shut, a distinct image of the object will be obtained upon the screen, by adjusting the tubes V and K with the magnifiers, which is done by moving them backwards and forwards As the sun is always in motion, it is necessary to shift the place of the mirror NOP, so as to keep the reflected light coin cident with the axis of the tube. This effect may be produced in a superior nianner by adapting the solar mi croscope to a HELIOSTATE (see that article) or piece of clock-work, which drives the mirror continually, so as to make it always reflect the sun's light in one direc tion.
In order to use the microscope for transparent ob jects, take away the opaque box HILX, and insert the tube Y of Fig. 27. in EF. Place the slider, Fig. 28. in its place at n, a condenser, Fig. 29. into the opening at h, and the slider, Fig. 32. with the objects between the plates at m : then, having adjusted the mirror NOP as before, a magnificent picture of the object will he seen on the white screen.
The solar microscope now described, though possess ing all the advantages that can arise from mechanical construction, is still a very imperfect instrument, being liable to all the bad effects arising from the different re frangibility of light.
The only method of remedying this defect, is to cor rect the colour, either by using a combination of lenses for the purpose of forming the image, or to use a lens composed of differently dispersing and refracting me dia.