Albert Ott, Kempten. > 57 



12. A Theodolite (Tacheometer) (Fig. 4), latest construction, 

 Patented in Germany to the inventors, Messrs.Tichy and Ott; particu- 

 lary suitable for accurate and speedy work in land-surveying. 



The circles are divided on the 360 degrees system, but do not read 

 to minutes and seconds, but to -y^y degrees. Distances are measured, 

 by a new method, by means of a staff divided in logarithmic progression, 

 which has to be set up strictly vertical, two supports and crossed levels 

 being appended for this purpose. 



By this method distances are measured much more exact!}* than 

 is possible with other optical distance measuring instruments. 



In order to find from the slanting distance the horizontal distance 

 the altitude arc has, beside the ordinary graduation, logarithmic divisions. 

 By subtracting the altitude reading from the height on the staff the 

 reduced distance is directly obtained from ordinary tables of logarithms, 

 .and from this and the altitude the difference of elevation .between the 

 instrument and the stand-point of the staff can be found. 



13. A Theodolite similar to No. 11, but with rotating azimuth 

 and altitude circles, either reading by micrometer and lens, to Viooo de- 

 .gree on the 360 circles. 



A noticeable feature of the theodolites Nos. 11 and 12 is the form 

 of the stands supplied with them and the manner of packing the instruments 

 in the case. 



14. A logarithmic staff for Nos. 11 and 12. These staves are 

 made of lengths of 2.05, 2.55 and 3.05 meter for distances of 200, 250 

 and 300 meters respectively. 



15. A Surveyor's Drawing Board with table, Patented in 

 Germany to the inventors, Messrs. Tichy and Ott, for drawing with 

 accuracy and despatch tacheometric measurements made with the theodolite. 

 The angles may be drawn either to sexagesimal minutes or centesimals 

 of the 360 degree or 400 grade system. The distances are marked by 

 means of a puncturing-needle which slides along the divided ruler and 

 the points are encircled by means of a rotating lead pencil. 



(A detailed description of this apparatus will be found in the 

 catalogue of the Exhibition of the German Universities.) 



