104 REPORT — 1841. 



120 to 130 feet per minute; the velocity of the plunger is usually four-fifths of this 

 amount, or 100 to 120 feet per minute. Still a portion of the water, from one- third 

 to one-sixth, is raised at three-fourths of the higher velocity ; recently larger valves 

 have been placed below the plunger than above, with a view of equalizing the resist- 

 ance of the water on passing the valves. In commencing motion, after the state of 

 rest to which pumping engines are brought, it is possible a greater power may be 

 employed than is required to continue it ; still the term variable load, formerly adopted 

 by the writer of this paper, may be too strong. In an attempt to value friction by 

 the area of the rubbing surfaces of the packing of the plungers, it appeared the una- 

 nimous opinion of many of the best pitmen, that water could be kept from escaping 

 with less friction by means of twelve-inch than with nine-inch packing, in a twelve- 

 inch plunger-lift, — a circumstance that requires attention, not only in this, but pro- 

 bably under numerous other conditions of friction calculations. In regard to the 

 effect of expansion on the pitwork in producing a variable strain during the load, it 

 was observed, that with twelve times expansion on an engine recently erected, of 

 Watt's construction, including clearance steam, the variation was found by an indi- 

 cator to be as 8 to 1 at the end of the stroke ; but that in a new engine with combined 

 cylinder, by Sims, in which the steam is expanded twelve times, viz. three times in a 

 small cylinder, and subsequently four times in a larger cylinder during the out- door 

 stroke, this power being converted into a constant quantity in-doors by means of a 

 balance, the variation of pressure would be about as 2 to 1 only ; and that in Horn- 

 blower's or Woolf's, if worked with high steam, under the condition of twelve times 

 expansion, including clearance steam, the variation might be roughly taken as 3 to 1 ; 

 — that the commercial part of the question of more or less expense in engines or 

 pitwork, would determine the relative advantages, on the whole, of each engine for 

 lifting water from deep mines. It seems that expansion has not been carried out to so 

 great an extent when the load is near the end of the beam, and when the enormous 

 balance weights, usual in Cornish pitwork, are not required to be applied, though it 

 is obvious that this condition causes less pitwork friction. 



On an improved Sight for Rijles and other Fire-arms. By Chahles 



Thornton Coathupe. 



As a substitute for the ordinary steel-leaved rifle sight, whose heights are regulated 

 for certain definite ranges (between which an imaginary allowance for the correct 

 elevation is all that can be effected), Mr. Coathupe recommends another upon a dif- 

 ferent principle, equally simple, and by which any elevation may be readily obtained 

 with accuracy, commencing with the lowest, or point-blank range, and ascending by 

 the least possible increments to the extreme range for all useful purposes. 



It should be constructed by first forging a piece of iron, which, when filed up flat, 

 and square at the edges, shall furnish a wedge, or inclined plane, from six to eight 

 inches in length, and from three-eighths to half an inch in width, having its thicker 

 extremity about three-eighths of an inch, and its thinner end about one-sixteenth of 

 an inch in thickness. 



Upon this inclined plane a piece of steel, of similar length and width to that of the 

 inclined plane, but of uniform thickness throughout, and having its edges filed so as 

 to exhibit a dove-tail section, must be fixed, the wider surface being uppermost. 

 Upon this dove-tail plate a steel sight, with a small notch filed in the centre of its 

 upper edge, must be fitted so as to traverse steadily from end to end. The dove-tail 

 plate may be attached to the inclined plane by means of gunsmiths' solder ; and when 

 thus fixed, a narrow groove must be filed longitudinally through its substance, com- 

 mencing in a median line upon its upper surface, the bottom of the groove being par- 

 allel to the base of the inclined plane. The whole must then be affixed to the rifle 

 barrel, in a line corresponding with the axis of the bore, by means of three steel screws, 

 whose heads must be countersunk. 



It is evident, that if the upper edge of this traversing sight, when at the commence- 

 ment of the inclined plane, be so adjusted to the perpendicular heights of the in- 

 clined plane, and of the sight near the muzzle, that a line passing through a central 

 point in each shall be parallel to the axis of the bore, this will be the position for the 

 point-blank range of the rifle ; also, that if the traversing sight be pushed further 

 along the inclined plane, the angle of elevation, and consequently the range, will be 



I 



