SEC. lo. GEOGRAPHY. 



investigations as to the relative value of the vernier and microscope readings 

 of five divisions, and, secondly, for observations upon the magnitude of terres- 

 trial refractions and their variation with temperature and the pressure of the 

 air. The exhibitor has not yet described his instrument, because the number 

 of observations made with it is still too small to allow certain results to be 

 deduced from them. The instrument, however, perfectly fulfils its purpose. 



3074. Repeating Theodolite, horizontal circle, 15 cm., with 

 covered division circle of altitude 12 cm. A. Bonsack, Berlin. 



Repeating Theodolite. Both circles are divided on silver ; the first 

 into i with two verniers to Imlf minutes ; the second into ^ readable to one 

 minute by one vernier. The telescope is adapted for distance measurements 

 by a method invented by me, and which has been strongly recommended by 

 Herr S. "Woyike, who used it in operations on the Ostbahn. With the stand. 



3075. Theodolite with Microscopes on the horizontal 

 circle. J. W. Breithaupt and Son, Cassel. 



Theodolite for Geodetic purposes. Horizontal circle 20 centimetres in. 

 diameter, with microscopes showing two seconds directly ; the fine division 

 is protected by a cover; the verniers of the vertical circle show 10 seconds ; 

 orthoscopic telescope for Durckschlagen and reversal, with arrangement 

 for distance-measuring and with reversion spirit-level and level on the axis of 

 the telescope. The circles may be shifted for Satz observations. The micro- 

 scopes have parallels and reversion scales on glass. This theodolite belongs 

 to the Koyal Forest Academy at Miinden. 



3076. Pocket Theodolite. 



J. W. Breithaupt and Son, Cassel. 



Capable of employment, on account of its small dimensions, in very con- 

 fined spaces, in mines, &c. 



3077. Francis* Patent Pocket Theodolite, made by 

 Negretti and Zainbra. George Francis, C.E. 



The improvements claimed for this invention are, 1st, its portability and 

 cheapness ; 2nd, its simpieness and easy application ; 3rd, the proportional 

 increase of length between the sights for dialling ; 4th, it is less liable to error 

 in taking horizontal angles ; 5th, its adaptability for taking the angle of an 

 underlie or gradient; 6th, it requires little or no adjusting ; it combines with 

 the theodolite a clinometer, protractor, and plotting scales for reference from 

 1 to 60 feet to the inch. 



At each setting of the instrument, the following observations can be taken: 

 1st, the horizontal angle of the back and forward drafts to ^th part of a 

 degree ; 2nd, the magnetic bearing to ^ ; and Srdly, the rise or fall in the 

 draft to ^ and also in inches to the fathom for perpendicular and base. 



3079. Tachymeter (theodolite), with stands. 



Ban Deputation, Hamburg. 



3079a. Theodolite (Tachymeter), from the mechanical 

 workshops of Dennert and Pape in Altona. 



This was specially constructed by these mechanical engineers according to 

 the directions of the Survey Department for the measurement of distances 

 and heights, as well as for geodetical purposes. The arrangement has been 



