Hassler’s Repeating Theodolite. 258 
Mr. Patten, if 1 omitted to bear testimony to the seeeeoer 
his work, not only in the construction of this, but a 
other instruments for the expedition. The beauty a ac- 
curacy of the division, (an operation hitherto deemed by 
many impossible in this country,) would not pcan in com- 
parison with that of- European artists. He c t be too 
highly recommended “dl the patronage of the public. 
ur obedient servant, 
Cuartes WILKE 
Professor Silliman. Lieutenant U.S. Navy. 
Fig. 1 is a perspective view of the instrument. 
Fig. 2. The horizontal circle with its alhidades, &c. &c. 
rg. 3, The vertical circle with its alhidades, &, 
. 4, A section of the whole instrument. 
The letters < me perspective “ae answer to those of 
the sectional par 
a, a, a, are hice horizontal radii of six inches radius, in 
the ends of which are simple ier) ae which fit in 
sockets on similar radii, 4, 4,4, screwed to the top of a three 
legged stand, which serves as ‘the cn of the eget rertcn 
in the field. ’b, , is the horizontal or azimuth circle, of nin 
inches diameter, with a silver arch attached to the middle 
conical sete y, divid and re ad off, by means of verniers, 
o fifteen seconds. c, c, is the lower or standing at 
attacked’ to 5 ttie outer cenit: x, having four arms, three be 
dade, attached to the inner ates! centre, z, having four 
eh three of which bear verniers, the fourth a ‘clamping and 
tangent screw, for slow motion, on two of these arms are 
placed the hollow conical pillars, e, e, of an inch and a quar- 
ter diameter at their basis; to the top of Assit is fixed t 
Y’s, for the axis - the telescope, having vertical adjust- 
ment in one of th Sf, f; is the seine of twelve inches 
in length, with its eeibal hollow arms, g, 8; the pillars, e, e, 
are of sufficient height to allow the telescope to have a free 
motion through the vertical ; on one of the arms is fitted the 
vertical circle, h, h, of six inches diameter, with a silver arch — 
i etal collar, and read off by means of ver- 
niers to fifteen seconds, having two alhidades similar in every 
respect to the horizontal circle. 2, 7, is the imner alhidade, 
attached to and moving with the ialescoye; having four arms. 
