M I C li O S C O P E. 



223 



I'U < 



j<- mtt 



micro- 

 cope. 



id out certain theoretical advantages which lie 

 would be found in microscopes with six 

 lenses. Such a combination of lenses, however, has 

 been exploded, and we do not scruple to say, that there. 

 is no eminent optician in Europe who would construct 

 riocope in such a manner, unless the lenses were 

 >me modem eye-pieces, so as to correct 

 i rration. 



M. Acinus of >t. I'etcrsburgh proposed, in the year 

 I'ftrop. 1784,) to construct microscopes 

 w ith larjjc apertures of considerable length, irith Achro- 

 matic cbject-gUuiti. The great object of this construc- 

 tion was to permit light to be easily thrown upon the 

 object ; and in order to put his idea to the test of ex- 

 periment, he constructed a microscope, in which the 

 aperture of the object lens was about 1 inch ; the dis- 

 of the oliji'ct from the ol>jert-glass ~ inches, and 

 the length of i ument a little less than 



three I'n-t. The magnifying power was from GO to 70, 

 and therefor* the focal length of the eyc-glaM mint 

 have been about \ an inch, to M to roagnu 



' met. J hi* mttmiielit i said to have given 

 great satisfaction. The tame idea bad occurred long 

 before to our countryman Benjamin Martin, who, in 

 his description and MM of a polydynamic microeeope, 

 has shewn that the acbroaoatic perspective may be 

 easily applied for this purpose. 



Various improvements were made upon the micro- 

 scope by Mr. Cuff, Mr. Benjamin Martin, Mr. Adams, 

 and other opticians ; but as they relate principally 

 to the method of fitting them up, and of rcml< r.i.j 

 them more commodious anil universal in their applica- 

 tion, we cannot enter into any detailed account of their 

 respective improvement*, which will be better seen in 

 the account of the instrument* themselve*. 



Having thus given short account of the history of 

 the compound microscope, we shall now describe tome 

 of the mot interesting forms in which it has been fit- 

 ted up. 



I. Cuff't DoMe Cmutnclrd Microicope. 



Cnireoni. Thii instrument is represented in Fig. 19, where 

 pound mi- ABC is the body of the microscope, having an 

 ntruf. glass at A, an amplifying lens at B, and a 1.1 i^m'tirr 

 '* " crewel on at C, and shewn separately at Q. The bo- 

 dy of the microscope is supported by the arm DE, fix- 

 ed on the sliding >>ar F. The principal pillar a & is 

 fixed on the b bra-n foot d 'n scrcwel to 



i thogany pe<lestal XV, having a drawer to con- 

 tain all the app. tightened by a 



niillcc! hra-leil screw O, when the adjusting screw eg 

 i* used. ! i are laid upon the rtage ji ij, with 



a hole H in its centre, and the li^ht thrown upon them 

 by the concave mirrnr ('. 



The following are the different parts of the appantM 

 which accompany t hi- microscope : 



H .1 - concentrating the rays of the sun 



upon th< 

 L I tube open at each side, and having a 



ive silver speculum screwed to the 

 1' the tube for holding the lens K, with an inner tube, 

 ,.ards with a spiral spring. The 

 i the plates h and i. The 



lower end of P goe into tht- hole n in the stage. 

 The hollow part at * is intended to receive a class 

 tul, 



I a brass cone, which ii occasionally put in the 

 bottom of the cylinder P to intercept the light. 



S is a box, with a concave and a flat glass for con- Compound 

 fining small living insects. It is placed upon the Micro- 

 hole H. sc l'- 



T is a flat glass to lay objects upon, and u a concave ~ / ~~ 

 one for tii 



U u a pair of pliers and a sharp point ; and Z a 

 brush, as formerly described. 



\V is a round ivory box, for holding circular pieces 

 of mica, and rings for the sli> 



a small ivory cylinder, which goes upon the 

 pointed end of the steel w-ire O. 



M a fish-pan for holding small fi^he-, in order to view 

 the circulation of the blood. The tail is spread 

 across the oblong hole at the email end / . and tied 

 firmly by a ribbon fixed to it. The knob / is to 

 be put through the slit in made in the stage, and 

 the tail may be brought below the end C of the 

 microscope. 



\ is a wire, by which the glas* tubes are cleaned. 



In using this microscope, screw the proper magnifier 



to the end C, place the tube I' in the hole N, and slip 



the ivory sliders between the plates h and i. 



Make the upper edge of the bar 1)1. cuinc-ide with the 



division, having the vinie number with the magnifier 



used, and fix it firmly by the nut C). Light being 



thrown upon the object by the mirror G, apply the eye 



to the up|HT end of the microscope, and obtain distinct 



means of the adjusting screw eg. 



\Vhcn the ohjects are opaque, remove the tube P, and 

 having placed the object on a flat glass u under C, or 

 upon one end of the jointed pliers o p, screw the con. 

 cave silver speculum to the end of the cylinder L, and 

 'lit cylinder on the lower part EC of the tube, 

 so that the upper edge of L may coincide with the same 

 number as the number of the magnifier employed. Re- 

 flect the light ii.|-!i.\ i d from the mirror G upon the 

 speculum A, and it will I c xgain reflected from the spe- 

 culum upon the side of the opaque o!>j<-ct next the eye. 



1 1 . L'nitcrtnl Compound Microtcope. 



One of the mo*t complete mid commodious compoundcnivensl 

 mirnncopei i* represented in "here AH is thccompound 



body, the eye-glasses bci; :HM| in an inner sliding 1 "'" - 



liy w h:ch thrir di-tance from the glass at B can l>e"f." p "L ) . 

 increased or dimini-hed, and the magnifying power of '*' 

 the instrument altered. The Iwdy AH i attached by 

 screw to the arm CD, which may be moved through 

 a square socket over the object. The stapc N1S move* 

 up and down the square bar EF by means of the rack 

 and pinion M ; and this bar, with all its ccomu-inying 

 apparatus-, moves round a joint at the top of the : 

 pillar V, supported upon the three feet G, G, H 

 the aid of this joint, the microscope may be put into 

 horizontal, a vertical, or an oblique direction. At the 

 stage MS is a sliding brasa spring N, for confining 

 slips of glass, or large sliders, when the microscope w 

 to be used out of the horizontal position. The lens 

 U is intended to concentrate or modify the light re- 

 flected from the mirror G, and it may be adjusted 

 to a proper distance by means of two small screws, 

 one of which is seen at K. In candle light this lens 

 is of great use, and it may be tinned aside on a 

 joint when it is not required. Six magnifying lenses 

 are set in a brass wheel, screwed in a circular box P. 

 The wheel may be moved round its centre by the ac- 

 tion of the finger on its mdled-rim, and it /tops by a 



