938 AN ACCOUNT OF THE 
base. As the instrument answers as a transit, and 1s well known, there is 
_ the less occasion to say any thing, as to the manner of employing it. 
18. Tue base having been aligned and cleared, and large pickets, 
numbered regularly, driven into the ground, every 500 feet, T commenced 
the measurement on the 2d. February, by laying the first pair of rods in 
contact, with the wire of a plummet, brought carefully over a point on the 
picket, marking the extremity of the line. So many difficulties attended 
the operation at this early stage, while none of my people understood clear- 
ly what was required from them, that to lay this firsi pair of rods occupied 
me nearly‘an hour, although afterwards, when more perfect, ten minutes 
_ generally sufficed, and frequently the pair was adjusted and entered in six mi- 
nutes. I found that Iwas even myself a little confused at first, before I had 
| completely settled the arrangement, by which I was to proceed in the different 
operations which i had to perform. Jor these reasons I was not sorry to 
find afterwards when I came to observe the angles, that it was necessary to 
reject a small piece at the commencement, I had, after marking out the base, 
wished to add to it. T’his piece was remarkably low, the declivity being 
about 5, and when the circle was set up, it was found impossible to view 
the flag staf at the other extremity. In the first instance, the base had 
been marked out, and the extremity fixed, as finally chosen, and in going on 
with the measurement as commenced from a point 450 feet hack, it was 
most carefully noticed, by what quantity, the end of the last of the rods fall- 
ing here, overshot the large picket, which had been driven into the evound, 
to mark the originally chosen extremity. ‘The measurement of this 450 
feet, which comprehended more difficulties than any other portion of the 
