746 SEC. 15. - GEOGRAPHY. 



The Topographical Department of the Royal Land Survey has exhibited 

 a telescope ruler, which is now introduced by the Department. It has double 

 verniers and a reversing telescope, and is also furnished with a double bubble- 

 tube, rendering the instrument very useful for levelling. The distance-measure 

 is removable, but so contrived that no screw is visible outside, so that nothing 

 can act upon it. 



3082b. 6-inch Transit Theodolite. G. W. Strawson. 



3082c. 5-inch Transit Theodolites (2). 



G. W. Sir aw son* 

 31O6. Repeating Theodolite. 



Meissner, Berlin (fl. Muller and F. Reincckc). 



3072. Distance and Altitude Measuring Theodolite, by 



Dennert and Pape, Altona, with stand. 



Prof. Helmert, Aix-la-Chapelle. 



The theodolite is intended for topographical surveys. The division of 

 the circles is so fine that frequently the reading of one index will suffice, its 

 position being appreciable to 1 minute with the lens, without the employ- 

 ment of the vernier. As the stand has great stability, the vernier arm is not 

 movable together with a spirit level, but both are fixed. 



3079. Tachymeter (theodolite), with stands. 



Ban Deputation, Hamburg. 



3O79a, Theodolite (Tachymeter), from the mechanical 

 workshops of Dennert and Pape, Altona. 



Royal Prussian Ordnance Survey Department. 



This was specially constructed by Dennert and Pape, Altona, according 

 to the directions of the Survey Department for the measurement of 

 distances and heights, as well as for geodetical purposes. The arrange- 

 ment has been such that, besides lightness, sufficient stability is afforded for 

 work of such a nature. The circles are divided to 10', so that they can be 

 read without the aid of the vernier to 5', and that the operator is not obliged 

 to leave his place during the work for the purpose of reading at the circles. 



For distance and height measurement, after the centre horizontal thread 

 has been adjusted to any point of the levelling staff, and the readings taken, 

 and the difference of the readings for the two threads, as well as the reading 

 of the centre thread, is noted in the field book. 



For the observation of the line of direction of other stations, the circles are 

 fixed by the clamping screws, and the exact adjustment obtained by means 

 of the micrometer screws. 



3089a. Topographical Instrument, called "Cleps," 

 constructed by Messrs. Salmorraghi, Bizzi, and Co., Milan. 



M. Antoine d'Abbadie, Member of the Institute, 120, Rue 

 du BaC) Paris. 



This altazimuth has three peculiarities : 



1st. The telescope is very powerful for its size. 



2nd. Through the small transverse eyepiece the observer may read at 

 the same time the horizontal and the vertical angle ; the divided 

 circles, completely covered, being lighted from, above. To save 

 time, there is neither microscope nor vernier, the angles being 



