MEASURING THE EARTH'S SURFACE. 243 



uttered his historical " Eppxir si tnnove," has been parallel to the ad- 

 vance made in all other branches of scientific knowledge and methods 

 of investigation. 



The first notions concerning the form of the earth were that its 

 form was that of a tablet, ending abruptly at its extremities into 

 what would be considered the abyss, which could not be reached by 

 man. The idea that the earth was nothing but a plane was abandoned 

 before the beginning of the Christian era. The earlier attempts at 

 calculating the size of the globe were based on astronomical obser- 

 vations. It would be difficult to-day to say within what degree of 

 accuracy the figures then obtained could have been relied upon, as the 

 units of measurement used by those pioneers have been lost and could 

 not be compared with the units now in use. 



One of the earlier attempts at obtaining the actual length of the 

 earth's meridian by direct measurement of a portion of the same was 

 made in the sixteenth century by a French doctor. The means em- 

 ployed, although very ingenious, would be considered perfectly clumsy 

 and inadequate by the modern scientist. There was in this early 

 measurement no attempt at mathematical precision as understood in 

 the present century, and, considering the simplicity of the method em- 

 ployed by the doctor, it is only to be wondered that no greater error 

 was obtained in its final result. The measurement consisted simply 

 in driving from Paris to Amiens, and counting the revolutions of the 

 wheels of the carriage, and from the number of revolutions of the 

 wheels obtain the distance between the two cities, which could serve 

 as a basis for calculating the length of the meridian. Of course, this 

 calculation could not by any means be considered accurate, but, taking 

 into account the means employed, the result obtained has been sub- 

 sequently found to be wonderfully precise. The most curious thing 

 about it is, that what would now be considered grave errors and inex- 

 actitudes were so distributed that they almost compensated each other, 

 and the dimensions then obtained show only slight differences with 

 the dimensions given by the most recent measurements. Thus chance 

 (and no better name could be found) permitted of the same results, 

 with only a small final error, being obtained with that crude method, 

 that are now obtained with the most precise instruments and with 

 the most complicated calculations, 



Geodetical triangulation is, like many of the other branches of 

 scientific applications, essentially a child of the modern era. It is not 

 older than the seventeenth century ; the first application of geodet- 

 ical triangulation to the measurement of an arc of the earth's merid- 

 ian having been made in Holland at the beginning of that century. 

 It was followed by similar measurements in England and in France, 

 but in all these measurements the arc measured was never greater than 

 two degrees, and the importance of such measurements on the ques- 

 tion of the length of the earth's meridian could therefore not be con- 



