38 



Max Kohl, Chemnitz. 



made up of two parts which are at right angles to each other, a rectan- 

 gular reflecting prism being placed between ocular and objective 



at the point of intersection of the 

 axes. The light reflected by the small 

 prism in the oculnr parses through the ob- 

 jective and meets the mirror attached to 

 a semicircular or annular magnet : it is- 

 then reflected by this mirror and returns 

 to the ocular. The image of a cross line 

 placed below the small reflecting prism 

 is in this manner thrown upon the ocular 

 scale and the slightest movement of the 

 mirror rendered visible. The sensibility 

 of this instrument is exceedingly great 

 and may be regulated to a certain extent 

 according to the requirements of the case 

 by means of two controlling magnets. 

 When adjusted for maximum sensibility 

 a deflection of one division of the scale 

 represents about 0.00000018 Amp. r 

 when adjusted for its minimum sensibility 

 0.0000013 Amp. The galvanometer is 

 exceedingly portable, being provided 

 with a most effective disengaging catch 

 and having all its sensitive parts well encased 

 and protected. The galvanometer is, therefore, 

 principally used for testing cables and insu- 

 lations, and is unquestionably the best existing 

 instrument for this purpose. 



6. Beetz's Lecture 

 Galvanometer. (Fig. 6.) 



This galvanometer is made in 

 a most convenient form for lecture 

 demonstrations. It is provided 

 with a controlling magnet so as 

 to render it possible to always 

 direct the scale towards the au- 

 dience and its scale is divided so 

 as to be distinctly visible from 

 the distance. A special feature 

 of the instrument is the facility 

 with which the coils can be inter- 

 changed. Two differently wound 

 coils are supplied with the in- 

 strument. 



Fie;. 6. 



