THE FIRST DAY'S WOBK 25 



lations of the thumb screws and a few mild expres- 

 sions of self-exhortation, finally succeeded in fixing 

 the junction of the two cross hairs on the lens upon 

 a point on the rod. When he had noted down a few 

 figures he waved Conway to desist and the latter 

 thereupon marked the spot where the base of his 

 stadia had stood with a stone and sat down to rest 

 until we came up. 



How he did it I don't know, for I'm not and never 

 hope to be a mathematician, but by consulting the 

 scale on the arcs of his instrument and a little leather 

 covered book of tables and formulae, and after mak- 

 ing sundry feverish calculations on a pad of scratch 

 paper, Wallace presently announced that we had 

 progressed (by shot) two hundred and three feet, 

 and that the elevation of our next set up where 

 Conway was would be eight feet higher than where 

 we stood. The alidade, it appeared, had the mys- 

 terious faculty of revealing both distance and in- 

 crease or decrease of elevation to the operator. 



And this was not all. We were to see now the 

 reason for placing the corner of the base of the ali- 

 dade on the point on the township plat which repre- 

 sented our present location. With a finely marked 

 rule Wallace measured the distance of the shot, 

 changed to the scale of the plat, along the base of 

 the alidade and stuck a needle-pointed instrument 

 like an awl into the plat at a point corresponding to 

 the spot where Conway sat. Then he drew a pencil 

 along the paper, between the two points, using the 



