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MISCELLANEOUS INTELLIGENCE. 

 § I. Mechanical Science. 



1. Tulley*s New Catadioptric Microscopes. — Mr. W. Tulley, stimu- 

 lated by the example and success of Amici, has invented a reflecting 

 microscope, the optical principle of which is, we believe, entirely 

 iiew and original ; the objective part consists of an elliptic metal, 

 and a perforated plane one of corresponding dimensions, forming 

 an angle of forty-five degrees with it. A section of a cylinder is 

 introduced into the hole of the plane metal, in such a way as to 

 allow light to pass towards the elliptic metal, but to exclude it in 

 every other direction, so that no false rays can enter. 



The manner in which the instrument operates is as follows : — 

 The object to be viewed is placed nearly whole in the plane, through 

 which its rays diverge towards the elliptic metal, from which they 

 are reverberated to the plane metal, which reflects them at right 

 angles to the eye-piece, by which the image they form is viewed in 

 the usual way (the object of the section of the cylinder is to exclude 

 false light). This instrument has its good and evil properties, like 

 all others. It has been duly executed by Mr. Tulley, and may be 

 considered in its optical principle and its performance, equal to that 

 of Professor Amici, over which, indeed, it possesses the advantage 

 of being capable of receiving an unlimited angle of aperture. The 

 objection to it is that the diagonal metal does not permit the ap- 

 proach of an object to the focus of the elliptic one, with the facility 

 necessary for practical purposes. Only very small objects can be 

 viewed, which must be mounted in a particular manner, having to 

 be introduced as it were into the external part of the hole in the 

 plane, where no latitude of motion can take place ; sliders, 

 aquatic live boxes, &c. are wholly inadmissible : these defects, will 

 we are afraid, confine this instrument to the cabinets of the curious. 

 There is a great difficulty in executing the plane metal, for that 

 part immediately about the hole must be perfect, and the sharp 

 edges of the aperture are a great obstacle to correct execution 

 (which, however, has been conquered by Mr. T.). There are impedi- 

 ments also in the adjustment of the plane, which is apt to lose its 

 figure, being made as thin as possible to admit the approach of the 

 object to it. 



The other microscope forms its image by one reflection only. 

 Opaque objects are mounted upon a small arm, and presented to 

 the focus of an elliptic metal inserted at the end of a tube, at the 

 other extremity of which the usual eye-glasses are placed, while the 

 illumination is effected from an aperture in its side. 



Transparent objects are illuminated by means of light, furnished 

 by a small plane metal placed diagonally behind them, being in 

 fact exactly similar to that which is employed in the Amician 



JULY— SEPT. 1828. O 



