Topographical Sui-vey of Spain. 361 



must necessarily have, viz., distortion in form and distortion in area, 

 are equally objectionable, the distance of the point of projection adopted 

 by Sir Henry James in his geometrical projection of two- thirds of the 

 sphere, will, for the projection of a hemisphere, give tlie least possible 



each other, one may be taken to represent the plane of projection for the 

 concave hemisphere above it, and the point of sight or projection is at 



Its circle. It is now demonstrated that this is the best possible projection 

 for a hemisphere, and it should therefore be adopted by all geograplicrs. 



2. Topographical Survey of Spain. — We learn from our correspond- 

 ent, M. Coello, the accomplished geographer, who is now directing the 

 typographical survey of Spain, that the following additions to our sci- 

 ence have recently been made. 



During the year 1861 persevering progress has been made in the great 



' I the chains of the triano'les of the first order have already been studied, 



L'hechain 



s of the meridian of Madrid, both to the north and to the 

 » of that capital, have nearly all been measured, and will be comple- 

 ^^-u oefore the end of the present year. 



. The parallel of Madrid to the west has been finished as far as the fron- 

 tier of Portugal; and the measurement of the triangles of the parallel 

 of Ciudad Real to Badajoz has been commenced. The triangles required 

 to complete the spaces to the west of the meridian of Madrid have been 

 laid down as far as that of Salamanca. 



The triangulation of the second order is finished for the whole province 

 of Madrid, as well as that for a part of the adjacent country. We are 

 now only waitintr for the results of the last calculations for compensation, 

 ^^liich have just'been completed, in order to fix the length of the great 

 Jase of Madridejos, and begin the long calculation of the work which 

 flas been done. 

 ^.Thisyear these different undertakings will^be ^^"[j^^^f^^^^f j^|g;^^' 



*ith accuracy the elevation of Madrid above the Mediterranean, pre- 

 sumed at present upon the most received existing calculations to be 660 

 Qietres, which is, perhaps, within ten inches of the truth. 



The topograph ical labors thus undertaken in the province of Madrid 

 ^^'11 be continued during the year. The corresponding land registration 

 ^''11 at the same time be proceeded with, and the levels will be very care- 

 fully taken. ,, .,,. 

 . The maps are on the scale of xirVtr. and «^' tU fof cities and buildings, 

 file classifications, territorial valuations, and dispositions in the public 



The topojrraphv is executed with very great accuracy. , ^ „ 



, Durin|the past vear a portion of the Tagus, and its tribiitary the Gallo, 

 lias been mapped to form a portion of the hydrography ot bpam. 



