238 SCIENTIFIC APPARATUS. 



The construction of charts and maps is a branch of geo- 

 graphical work which received improvements in proportion as 

 the observing instruments were made more perfect. While a 

 chart was a necessary part of the scientific apparatus for an 

 explorer, the chief result of his work was to extend and improve 

 it ; and as the more exact instruments continued to fix positions 

 with greater accuracy, so the delineation of coast-lines became 

 more correct. 



Thus the history of geography becomes very instructive. 

 While, on the one hand, the inspection of a series of sextants, 

 and of compasses of different dates, will exhibit the inventive 

 talent which was brought into play as ever-increasing demands 

 were made upon it, and the new adaptations which were gradu- 

 ally developed ; on the other, the examination of a chronological 

 series of charts will show the effect which improved scientific 

 instruments had upon their construction, and also the gradual 

 process by which succeeding generations of cartographers have 

 developed new ideas, and more graphic methods of delineating 

 the features to be exhibited. 



The character of maps varies according to the uses that are 

 required irom them; from the rough sketch of the pioneer of 

 discovery in a previously unknown country to the elaborate map 

 prepared as an aid to the calculation of the valuation of land for 

 taxation, or as the means for settling questions of property or 

 jurisdiction. f 



The maps of the Ordnance Survey of the United Kingdom, 

 and of the Revenue Surveys of India are of the latter class. 

 For the United Kingdom there is a topographical map of the 

 whole country on a scale of one inch to a mile (^ sbu), and there 

 will be county plans on a scale of six inches (TT^TI)> an ^ parish 

 plans on a scale ol twenty-five inches ( ? F\n>) to a mile > tne latter 

 only for cultivated districts in England and Scotland, not already 

 finished on the six-inch scale. In 1871 the detailed plan of 

 London was completed on the five-feet scale, drawn on 326 sheets. 



