III. MISCELLANEOUS. 623 



and, in every position, the micrometer work can be placed and reversed 

 without difficulty. The screens serve at the same time as bearers of the 

 magnifying glasses, so that every shadow on the nonii has been avoided. 



The circular divisions are executed on the exhibitor's own machines, which 

 have also the requisite exactness for large instruments with microscopical 

 division. 



The tripod stands of the three theodolites (Nos. 3056, 3057, and 3058) 

 have all purposely been chosen of different arrangements. 



3057. Small Repeating Theodolite, horizontal circle gra- 

 duated scales of 10 cm. diameter, divided on silver in 1, with two 

 verniers, reading minutes, with glass cover, movable magnifier, 

 with diaphragms. Vertical circle 10 cm. diameter, in silver in , 

 with double verniers reading minutes, with telescope of 23 mm. 

 aperture, 16 cm. focal distance, three micrometers -with spiral 

 springs. On the alhidada a spirit level ; a second for placement 

 on the telescopic axis ; a third for levelling on the telescope, to 

 be placed upright or turned over in both positions. 



Frerk and Son, Hanover. 



The repetition theodolite is a very complete instrument, which occupies 

 little space. The water-level on the telescope axis serves essentially for the 

 examination of the normal position of both axes. But as it forms a cross 

 with the alhidada-level, it is very easy, by means of both, to adjust the in- 

 strument horizontally, without necessitating any turning of the axis. The 

 correction of the telescope socket has been arranged according to a new and 

 simple manner. 



3058. Small Theodolite, horizontal circle graduated scale 

 10 cm. diameter, on silver in J, two verniers, indicating minutes, 

 two movable magnifiers, with diaphragms, altitude circle 8'5 cm. 

 diameter, with a double vernier indicating minutes. Telescope 

 23 mm. aperture, 24-5 cm. focal distance, two micrometers with 

 springs. In the centre of the alhidada, box level. 



Frerk and Son, Hanover. 



This small theodolite is also very compendious, but more simple, and of 

 quite a different form and construction. It is frequently constructed for 

 polygon measurements, and for use in forests. The holders of the magni- 

 fying glasses throw no shadow on the nonii. The encased water-level 

 can be easily taken out. The axis rotates with a hard glass point on a 

 regulating hard screw. The adjustment on the stand is as far as possible 

 without tension, but so that the plumb line is always hanging exactly in the 

 line of extension of the rotatory axis. All plumb lines can be suspended at 

 pleasure, either long or short. 



3059. Large repeating Theodolite, with arc and altitude 

 circle, divided into ^ ; with verniers 10 sec. for direct reading to 10". 



Dennert and P ape, Altona. 



3060. Theodolite with circles of six and four inches. 



Julius Wanschajf, Berlin. 



This theodolite has been constructed (of greater durability than usual) for 

 making very accurate measurements. The division is not the exhibitor's ; 



