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of an Arc of the Meridian . 
between the plumb-line and arch would be continually varying ; 
a perplexing evil, and the cause of great inaccuracy. The sum 
of this contrivance consists, first, in one of the Y plates having 
a small piece of brass screwed flat upon it, with a roller or 
friction-wheel at its end, which reaches just high enough to 
meet the vertical surface of the pivot a small distance within its 
circumference; and, secondly, in the other Y plate having a 
small apparatus, consisting of a lever furnished with another 
friction wheel and a spring, at its other extremity. This last 
mentioned roller, from the spring's action, presses against its 
proper pivot, and thrusts the other against the fixed wheel. By 
these simple but ingenious means, the axis is always retained in 
its proper situation with respect to the Ys. 
To prevent the axis from bending, by the preponderance of 
the telescope and arches, Mr. Ramsden added braces and coun- 
terpoising weights. The braces are four in number, each being 
a hollow tube : they are fastened both to the axis and the tele- 
scope. Their principal uses consist in obviating the possibility of 
the telescope bending from accidental pressure, or vibrating 
when lightly touched. The method of preventing the tele- 
scope from sinking, or, in other words, the axis from bending, 
is by the use of levers and the abovementioned weights. These 
levers, two in number, are attached to the interior mahogany 
frame at top, the fulcrum of each being immoveable. At 
the end of each lever farthest from the tube, a weight is sus- 
pended, from a hook capable of being placed nearer to, or farther 
from, the fulcrum, at pleasure ; thereby affording the means of 
raising the other end of the lever up against the cone, with 
any required degree of force. That extremity of the lever, so 
pressing upwards, has two large friction-wheels, which apply 
