70 riiACTICAL EXERCISES IX GEOGBAPIIY 



may l)e convinced that if their o1)servations were minutel}'^ accurate 

 the size of the earth could be estimated from even so short an arc as 

 that which they can pace during a recess interval. If a hill rises 

 neai' tlie school theconvexit}' of the hill mav be taken to imitate the 

 rotundity of a little earth. Two parties stationed out of sight of each 

 other on the north and south sloi)es of the hill, and on a north and 

 south line, may detennine the sun's noon altitude with reference to 

 the slopes of the hill (whicli imitate the curved, level surface of a little 

 earth), and then measuring tlie arc between their stations, the size of 

 a small earth to which such a hill would fit ma}' be determined. In 

 the absence of a hill, a useful substitute may be provided in a school 

 yard t)y placing two tables or boxes in a north and south line fifty or 

 a hundred feetapart, tilting their upper surfiices away from each otber, 

 and then proceeding on the i)retense that the table surfaces are ])arts 

 of a little earth, whose convex meridian ma}' be indicated by the to})s 

 of a row of stakes l)etween them. The curved surface of a globe in a 

 school-room ma}' be used to explain the geometry here involved, but 

 outdoor work should not be altogether replaced by such indoor sub- 

 stitutes. Nothing can so well give the sense of the real great earth as 

 outdoor observations. 



Two schools can })rofitably cooperate to measure the size of the 

 earth. On a certain day agreed upon beforehand the midday alti- 

 tude of the sun is determined at each school. The length of tbe 

 meridian arc between the latitude circles of the two schools may 

 then be measured on a good map and the proportion of Eratosthenes 

 again employed to find the unknown quantity. If each school de- 

 termines its own latitude, the diti'erence of latitudes rei>laces the 

 ditt'erence of the sun's midday altitude on a given day, and then no 

 agreement as to the day of observation is necessary. AN by is it that 

 nature study of this kind, so appropriate to the inhabitants of a 

 rotating globe, is not introduced in our lower schools ? Is it because 

 of the supposed dilliculty or the actual simplicity of the necessary 

 observations; on account of a recognition or a neglect of their value; 

 on account of a confidence in the innate ability of young schcdars or 

 a mistrust of their powers ; or on account of preparation or lack of 

 ])reparation on the i»art of the teachers? To the best of my belief, 

 this is merely one of the many cases in which the real mental activity 

 of school children is benuml^etl by substituting recitations of words 

 for live performance. 



