THE FIRST DAY’S WORK 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 formule, 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 
