dl)pllcation of the Wave Principle in Steam Vessels. 8t

caused the diflbrence, both engines having ~one at, as nearly as possible, the same speed. In order that the statement just given may not lead to t:alse conclusions, it is nccessa~)" to state what where those minor differences in vessel and engine which each constructor adopted as tending to greater ctilciency. The wave vessel had a flatter floor, and considerably squarer on the midship section, which was (lone for diminishing the depth of water as wanted for her use. In the other vessel, the consideration of draft of water was rejected or overlooked, and a finer midship section taken, al- though with a larger draft of water. In one case, also, the rudders were considered as part of the length of' the vessel, and treated accordingly, and, in the other ease, rejected ti'om it. In the engines, also, although the diameters of the cylinders were identical, the stroke of the wave vessel was somewhat lo,,ger than the other, but the diminished effective diameter in the shorter stroke reduced lhem to nearly the same proportion. Thus liar, the experiments given only serve to prove that, practically, a consider- ably better result has been obtained by a steam vessel built on the wave principle, than a competitor built under conditions that are perfectly iden- tical, in so far as the public and the owners are concerned. But as re- gards the purely scientific question, I shall add t~vo other experiments with the wave vessel, which fim~ish data of a more permanent and precise na- ture-one at a higher, the other at a lower velocity:--

E,c/)O'imel~ls on lhe lVave Vessel I. Vt,loclty of ve~el , 15.1,1 mih,s all hour. [ IL Velocity of vessel, 16"50 miles an hour,

" of wheel, 18"t7 " I " of wheel, 21"20 "

I Slip, 3'03 Slip, 4 '70

"1 hc area of rn dsh p section mmerscd was 89.4 feet. The surface of vessel immersed 'was 3080'0 feet. The area of paddle tloats was 26'8 feet.

The conclusion which I deduce fi'om these last experiments is this, that, by means of the wave form, one may obtain a form of which the resistance shall be represented by R=~I~ A H S, instead of R = $ A H S , which is the lowest number given m any previous syslem of construction;~A, bring the area of midship section, H, the height due to the velocity of the vessel, and S, the weight of a cubic foot of water.~Proc. B~'it. dssoc.

Improvements i~ ]Fixed and Revolving Lights, being a .New Dia-CatoTtric Inslrument for Iacreasing the Intensily of the Light. By TIto.~As STE- vnNsoN, ESQ., F. R. S. E., C. E. ~

The author stated that this instrument is composed of three parts--a paraboloidal mirror, having the conoidal portion behind the parameter cut ofF, and its place supplied by a hemispherical reflector, whose centre thus coincides with tile focus of tile t)araboloid, while in front of the flame is placed an annular lens subtending at the focus of the paraboloid, the same angle as that which is subtended at that point by the greatest double ordi- nate of the reflector, and having its principal focus coincident with that of the paraboloid. This instrument should theoretically produce the most in-

* From the London Civil Engineer and Architect 's Journal, for November, 1849.

82 Civil Engineering.

tense light yet derived fi'om an), given flame, as it encloses and parallelizes each ray of the whole sphere of light, so that none are lost by divergence between the lips of the reflector, where, in the present arrangemen b not very much short of one-half of the Sight is lost.

In this instrument, the hemispherical reflector throws the light which it receives (viz., the posterior half of the sphere of light) through the focus of the paraboloid, and while the outer ring of this light is received by the para- boloid, and parallelizr~d by it~ the central cone is received by the annular lens, and is also parallelized. The outer ring of the anterior half of the sphere of ligbt is recei red directly by the paraboloid, and is parallelized by it; while the central cone of rays~ which, ia the present arrangement, is lost by natural divergence, is received by the annular lens, and is parallelized by it. Thus the whole sphere of light is economized. This combination ,.nay also be applied mutatis mutandis to the illumination of half of the ho- rizon of a fixed light, by means of a single light: the only diftbrence being the substitution of two truncated parabolic eonoids for the paraboloid, and a. refracting belt tbr the lens. Two of these instruments directed to oppo- site points of the compass would light up the whole horizon.

Another new form of lighthouse apparatus was also described, by which the whole sphere of rays can be parallelized by means of a hemispherical reflector placed behind the light, and an annular lens, and a series of con- eentrie totally-reflecting glass zones, also placed in fiont, and receding from the lens back to the relleetor. These zones are also new in themseIves, as they have the property of parallelizing divergent rays, not only in a ver- tical plane, like the zones in Fresnel's fixed lights, but also in every plane ~vhatever.~Proc. Roff. 5'cot. Soc. 3rts.

Exlracls fron~ the ./lnnud Report of the Board of Canal Commissioners of Pennsylvani% Jbr the fiscal year ending 2Fov. 30, 1849.

The Board of Cared Commissioners submit the following report of the operations on the several lines of canal and railroad of the Commonwealth, for the year ending the 30th of November, 1849.

The receipts and expenditures "were as ibllow:~ ~ECEIPTS,

For motive power charges, and for the use of State trucks on the Philadelphia and Colum- bia railroad, including tines and old mate- rials sold, • . 8"291,759"36

For tolls on the Phiiadelphia and Columbia RR. 290,991"01 $58"2,750.3"/

For motive power charges, and for use of State trucks on the Allegheny Portage railroad, in- eluding fines and ohl materials sold, 166,453"93

For tolls on the Allegheny Portage railroad, 54,012"63 . . . . . . . . 2"20,466;56

For tolls on main line of canal, including collections at out- let locks, bridges, and aqueducts; also, rents, fines, and old materials sold, 443,324.58

Carried forward, 1,246,541"51