Mechanical Science. 377 



beforehand, lie will find the distance he is from the light-house by 

 an easy and expeditious method, sufficiently exact for his pur- 

 pose. — N. M. Mag. xv. 503. 



5. Cuthbert's Reflecting, Compound, and Single Microscope. — The 

 instrument made by Mr. Cuthbert, of Bishop's-walk, Lambeth, has 

 been described by the Editor of the Technical Repository, who 

 gives it high commendation. Having also witnessed the powers 

 of this instrument, we have no hesitation in bearing testi- 

 mony to its value, as much for its estimated economy and the 

 facility with which any one may use it, as for the faithful and 

 perfect manner in which it exhibits objects. 



The reflecting part of this instrument consists of a concave 

 elliptic speculum, of six-tenths of an inch focus, and three-tenths 

 diameter, mounted at the farther end of a short conical tube, 

 which is screwed into the cylindrical body of the microscope ; near 

 to the concave speculum an aperture is made in the side of the 

 conical tube, through which the image of the object to be viewed is 

 received upon a very small plane diagonal speculum, and by it 

 reflected into the concave speculum, from whence it is transmitted 

 through the body and eye glasses, to the eye of the spectator in 

 a greatly magnified state. Upon the conical tube a triangular bar 

 is fitted at right angles to it, having a sliding carriage upon it, 

 with a very fine rack and pinion to adjust it accurately : and to 

 the carriage a stage, fitted up with a springing plate to hold the 

 sliders, with objects in them to be viewed, can be adjusted ; or the 

 stage can be removed, and an improved forceps substituted in 

 its place. Upon the triangular bar an illuminating concave 

 speculum, mounted in a swinging adjusting frame, can be slided 

 when required to concentrate the light in viewing transparent 

 objects. And also upon the conical tube, an illuminating lens, 

 mounted in a swinging frame can be fitted, to increase the light 

 in viewing opaque objects ; and which, as the object, however 

 highly magnified, never approaches nearer to the conical tube 

 than the tenth part of an inch, can be readily effected. 



The cylindrical body of the microscope is received into the cleft- 

 jointed socket of the usual telescope-stand, fitted up with a bind- 

 ing screw, mounted upon three folding legs, and furnished with a 

 turning joint for changing the position of the body from a hori- 

 zontal to a vertical one, or any intermediate one at pleasure ; the 

 joint is also mounted upon a cylindrical tube, sliding in another to 

 which the legs are screwed, thus permitting the body of the 

 instrument to be elevated or depressed, or turned in any horizontal 

 or other direction at pleasure ; and as it can also be turned round 

 in the cleft-socket, so it admits of every possible variety of posi- 

 tion ; and can either receive the direct light of the sun, day-light, 



