680 SEC. 15. GEOGRAPHY. 



paper, when the latter it is adjusted with its centre point under the corre- 

 sponding '.station point, according to the horizontal angular measurements, 

 and then all the altitude points based on this station are sketched on the 

 tracing paper, their levels being noted ; when all the altitude points have been 

 marked down, then the construction of the contours, commenced on the 

 assumption that the slope of the ground is uniform between two altitude 

 points, the position of the intervening contour lines, can be determined 

 by the construction of similar triangles; this operation can, however, be 

 avoided by the use of the instrument (3127a) devised for this purpose. If, 

 for example, the altitude heights marked 30. 5 m and 32. 2 m have been ascer- 

 tained, the difference of which amounts to 17 decimeter, the two contours for 

 31 and 32 metres will fall between these two points. The edge of the mirror of 

 the variable scale is applied to the two points ; the cylinder is turned until 

 17 parts of the division projected on the paper by the mirror fall between the 

 points ; the cylinder is then moved in the direction of its axis until the corre- 

 sponding divisional marks 30 . 5 m and 32 . 2 m have been reached, and the points 

 of section of this line with the contours for 31 and 32 metres are marked off. 

 A better general view of the surface of the country divisions is afforded by 

 the models produced from these plans. 



3229a. Portfolio, containing various publications ; viz. 



(.) " Vermessung der Stadt Hamburg, Verzeichniss der trigo- 

 " nometrisch bestinnuten Punkte mit Netzkarte, Hara- 

 " burg, 1848." (Survey of the city of Hamburg, table of 

 the trigonometrically determined points with reticulated 

 map of Hamburg, 1848), containing the rectangular 

 co-ordinates of the points in the town and the nearest 

 vicinity, with lithographed sketches, and division of 

 sheets. 



(b.) " Vermessung der Stadt Hamburg, Verzeichniss der trigo- 

 " nometrischen Punkte nebst Dreiieckskarte, Hamburg, 

 1872." (Survey of the city of Hamburg, table of the 

 trigonometrical points with trigonometrical chart. The 

 latter in a scale of 1 : 50,000.) 



(c.) " Nivellements und Hohenbestimmungen von Hamburg 

 " und Ungebung, ausgefuhrt abseiten des Vermessungs- 

 " bureaus in den Jahren, 1869-1872. Mit einer Karte, 

 " Hamburg, 1872." (Le veilings and determination of 

 the heights of Hamburg and its environs, executed by 

 the Survey Department in the years 1869-1872. With 

 a map, 1872.) 



(d.) " Verzeichniss von Hohenpunkten in Hamburg und Unge- 

 " bung, bestimmt durch geometrische Nivellements 

 " abseiten des Vermessungs-Bureaus in den Jahren 1869 

 bis 1872, Hamburg, 1872." (Table of the heights of 

 Hamburg and its environs, as determined by geometrical 

 levellings, executed by the Survey Department in the 

 years 1869 to 1872, Hamburg, 1872.) 



(e.) "Distanz- und Hohenmessung. Formeln und Tabellen 

 " behufs Aufnahme und Hohenbestimmung, u.s.w. Ham- 



