III. SURVEYING. 761 



3, from a single point ; 4, without any calculation ; 5, by a mechanical setting 

 out of the measured distances and heights in proportion upon the plane of 

 the measuring table ; 6, in any scale. 



3094. Distance and Altitude Measuring Instrument 



(telescope ruler), executed, according to the directions of Prof. 

 Helmert, by F. W. Breithaupt and Son, Cassel. 



Prof. Helmertj Aix-la-Chapelle. 



This instrument is designed for topographical surveys. It has a distance- 

 measure on glass ; the altitude-circle is furnished with two verniers, although, 

 as a rule, only one of them need be read off ; 'moreover, the position of the 

 index may be ascertained with the lens without the employment of the vernier. 

 A spirit level is movable, together with the vernier arm, a mirror enabling it 

 to be seen from the eyepiece. The instrument also has levels and adjusting 

 screws for the horizontal axis of rotation of the telescope, and parallel ruler. 



3095. Triangular Frism. 



Geodetic Institute of the Royal Polytechnic School, 

 Munich, Prof. Dr. von Bauernfeind. 



The Three-sided Angle Prism, invented by the exhibtor in 1851, serves 

 for the measurement and setting out of right angles, and depends upon the 

 deviation of light by refraction and total reflection. See Bauernfeind's 

 " Elemente der Vermessungskunde ," 5th edition, 1876, Stuttgart, F. G. Cotta, 

 Vol. I., pp. 37-39 and 164, 165. 



3096. Distance-measuring Frism. 



Geodetic Institute of the Royal Polytechnic School, 

 Munich, Prof. Dr. von Bauernfeind. 



The Distance-measuring Prism, also invented by the exhibitor in 1851 

 but not applied to measuring distances until afterwards, serves for marking 

 off isosceles triangles in which the equal sizes are definite multiples of the 

 base. It is used in the same way as the three-sided angle prism. See 

 Bauernfeind's " Elemente der Vermessungskunde," 5th edition, Vol. I., 

 pp. 29-40 and 167 (No. 4), and Vol. II., pp. 90, 91. 



3097. Fentagonal Frism. 



Geodetic Institute of the Royal Polytechnic School, 

 Munich, Prof. Dr. von Bauernfeind. 



The Five-sided Angle Prism, invented by the exhibitor in 1869, serves 

 not only for the measurement and marking off of right angles and half right 

 angles, but especially for the laying down in position of two inaccessible 

 points, or points which cannot be directly observed. It may replace the 

 prismatic cross Xo. 3098. See Bauernfeind's "Elemente der Vermessungs- 

 kunde," 5th edition, Vol. I., pp. 44-46 and 166-168. 



3098. Frism Cross. 



Geodetic Institute of the Royal Polytechnic School^ 

 Munich, Prof. Dr. von Bauernfeind. 



The Prism Cross was invented by the exhibitor in the year 1851, and 

 was then described in a separate memoir (" Das Prismenkreuz," published 

 by I. Palm, Munich). It is described with later improvements in Bauern- 



