AMERICAN RAlLR0A1),.,..rIL°URNAL- v6 83 to the limited weights passing under them; but this flexibility would be inadmissible in a railway bridge, and the continuity of the rail would be de- stroyed if a very small deflexion took place when passed over by a heavy locomotive. With a view to give this necessary rigidity, Mr. Brunel has in- troduced at every third part of the tube a stiff wrought iron girder, connecting firmly the tube to the roadway girders; and, with the aid of ad- justing screws, the suspension chains are pulled or stretched as nearly straightas desirable. Other diagonal chains connect these points, so that at whatever part of the bridge an engine may be pass- ing its weight is distributed all over the tube and chains by these arrangements. The tube is laid upon the iron standards, but is free to move upon rollers at the top of the masonry standard. The expansion on the hottest day yet experienced has not exceeded one inch. The tube is strengthened within by the introduc- tion ofdiaphragms or discs at every 30_.feet, which renders it both light and stifi‘. The roadway girders are formed of a deep thin plate of iron stiifencd at intervals at the top, it has a strong triangular cell to resist compression, and at the bottom a double plate of rivetted iron to re- sist extension. Small cross girders are rivettcd to these side girders diagonally. On these 4 inch crcosoted planks are fastened crossing them in the opposite diagonal direction. Eighteen inches of gravel are laid over this floor, and on this bed the ordinary permanent way on longitudinal sleepers. One roadway was opened for travel on the 19th of July last, the tube and other portions of the second part are ready to be put up. Annexed is a summary of the cast and wrought iron used in the bridge 3-- Tons. cwts. qrs. Wrought iron, in three spans of 100 feet each, double line . . .. . . .. . . 277 0 0 Wftluglll iron in the girders, floor- bearers, and other work of the main span of 300 feet, double line 278 6 1 Two wrought iron tubes, each 312 feetlon . . . . . . . . . . . . 302 1] 0 Wrought iron beam on the standard to support the tubes . . . . . . . . . . . . 5 0 Vertical trusses . . .. . . .. . . . . . . . . . 3'7 0 1 Tie girders to connect the caps of co111mns.... . . . . . . . . 10 0 Suspending links in main chains and diagona1s.... .. . . . . .. 256 5 2 Saddles at points of suspension roll- ers.... . . . . . . . . . . . . . . 41 10 1 Adjusting screws . . . . . . .. . .. .. 2 10 0 Rollers of main tube . . . . . . . . . . . . . '7 1'7 3 Rollers of girders . . . . . . . . . . . . . . .. 2 11 3 Bolts........................... 3 15 0 Total wrought iron.. .. .. .. ..1231 2 2 . 1 , Tons. cwts. qrs. Cast-iron bed plates for trusses . . . . . 24 6 1 “ standard.... .. .. 128 6 O “ caps for columns and par- apets....‘......,....i... 0 “ cylinders in the support- ingpiers.............. 830 0 Total cast iron,.». . . . . . . . . . . . . 1003 12 1 3?.-ii’l‘£‘..’§f. T’f‘?’.‘II:2 33% 13 i } 2934 14 4 Masonry in abutment and pier, 3240 cubic yards. Total estimated cost of the bridge when entirely completed, £65,420. A number or ingenious arrangements are con- nected with the bridge to ensure elements of strength and rigidity in the structure. Among these may be mentioned the cast iron ring or circle attached to the ends oi the tube to prevent collapse; to the wedges introduced under the vertical trusses to ad- just the exact tension upon the-‘cha"ih’;Tt‘0'£li‘e curve? given to the tubes themselves, increasing their strength; and to the roller-boxes under the vertir-.al3 trusses, by which means the road girders are main? tained in a position to expand or contract independ- ently of the movements of the main tube. A The Mountain Lake Water Company of San F1-itnclsco. New York and Boston boast the engineering skill and costly works that have supplied them with that most important acquisition for city salubrity, pure water; and San Francisco Will, we hope, soon; be able to point to the abundant streams derived from her mountain springs and lakes. indeed we may entertain the hope that this will be a precursor to, other works of internal improvement in our El Do- rado State, and that the valley of the Sacramento, and San Joaquin may be traversed by railroads. even before California is connected with the two; iron arms that now are reaching forth to bind her, on the one hand with the Gulf of Mexico, and on the other hand with the Great Lakes and the St. Lawrence. The Mountain Lake company was organized on the l4th'August, 1851, under the general corpora- tion act of California, and a grant ol"the city of San Francisco to lay down pipes in the streets ol that city for 530 years, and an exclusive privilege for the term of 5 years from the 1st January, 1853, on condition that the corporate authorities of San Francisco shall use the water Ior extinguishing fires and also that after the‘ completion of the works, the supply shall not fall below one million of gallons daily. We learn lrorn the report of the Engineer, Henry S. Dexter, Esq., that the Lake is on the line of Pa- cific St. San Francisco, produced, and 3 miles and 2'25 rods distant from the corner of that street and Kearney street. On the 1st of‘Dece'mber, after two dry seasons, the surface of the lake’ was 123 '76-100 feet above Pacific wharf, and its area '72; acres.-«- The average depthwas 16. When full, the Lake has an available depth of 24 i'eet,”,and an area of 10; acres. It is situated in a basin surrounded by hills, some rising 300 feet above ‘it, and receives the drainage of a considerableextent of country.-, There is no visible outlet, thcrebcing about 300 yards from the head oi the ravine through which the brook flows, which discharges the percollating, waters of the lake. ' This ravine is} of a mile ' long, and has an average width of 100 yards. The hills skirting it are higher than tl1e,Lake, and the ridge separating the lake from the ravine is 18 feet; above the surface of the lake. Of course to render the water available for the supplyot‘ the city, it is necessary to intercept the flow of the water through the ravine, it is proposed to effect this by running a puddle wall and ditch across the ravine, and car- ry it as high as the surface of the water. The wall , is to be carried down to the hard pan orother strata impervious to water, and in its centre a row of sheet piling composed of 3 inch red wood planks sawed for the purpose and battened with inch red wood boards is to be inserted. At the lake two powerful steam engines are to be erected, forcing the water from the lake to a ‘distributing reservoir on Cannon Hill, in the neighborhood of the city. The pipe connecting this reservoir and the pumps is to be 16 inch bore. 1.} inches thick for the first 9,100 feet, and decreasing in thickness towards the summit.——- The bottom of the reservoir on Cannon Hill will be 360 feet above Pacific wharf, and 236 above the lake surface, the distance of Cannon lHill”fr'om ‘*1‘ the lake is about 1;, miles, and 2; miles from the "corner of Pacific {and Kearney streets. The cost of pipes, engines, reservoirs, etc., by this plan, is es- timated at $459,453. Another plan dispenses with pumps, and conducts the water from the lake to a distributing reservoir, at a level of 107 feet above f Pacific wharf, on the slope of a hill at the North ' Beach. The estimated cost of this line is $392,971. The estimated gross income for the year 1852, is set down at $10 a month, for 3,000 houses $360,000, and for 1853, for 5,000 houses $600,000. The lake forms a species of natural reservoir, and is fed by springs—-the main body of its waters are supplied by the lower strata passing through the adjoining hills, and extendingto the high range on the opposite side of the entrance to the harbor.-— The present outlet forms a rapid brook, the dis- charge of which is estimated at from 8 to 10 million gallons daily. A similar lake in the vicinity called the Lagmta H09Ld(b and 200 feet above the Moun- tain lake, can be added to it in case the supply is not suflicient. This, it is estimated, will furnishtt to_5, million of gallons daily. V _ t Thus at an expenditure of less than $500,000 the city of San Francisco will be supplied with pure and wholesome water. An almost equally import- ant considcration is the protection of the city, and the mcrchandizc of which it is the depot from de- struction by tire. The numerous destructive con- flagrations that have swept over that city destroying millions of property, show the necessity of an abun- dant supply of water. Its’ exposure to strong winds springing up daily, has hitherto rendered the most solidly constructed stores and warehouses insecure, and it is only by the introduction of -uniailingland copious streams of water that exemption can be hoped for. The works which are destined to secure this end must prove as profitable as they are indis- pensable to that capital of the gold region, and pro- bable centre oi the tuture mighty commerce of the Pacific basin. Mississippi and Chicago Railroad. , We learn, says the Chicago Tribune, that the party of Engineers, appointed to survey a line tor the Mississippi and Chicago railroad, have reach- ed the Sumrnit,—about twelve miles from the city, ontheir way to this point. We are informed that the surveys show a much more favorable grade than was expected. The survey is through Lock- port, to touch which requires scarcely any diverg- ence iroma direct line. It is rumored that the parties interested are try- ing to make arrangements for the sale of that por- tion of the Rock Island and Chicago road, lying between this city and Juliet, to the Mississippi and Chicago company, and that the lattcrdwill, next year, construct a mat of track irom Jolict to La. Porte. me an ,- . l ‘L V . V -in k I .. ‘J! I-Ioole, Sta.n1forth~ & '00., MlNERVA WORKS, . SI-IEFFIFLD, Steel Converters and Itefinere; ‘.11 Manufacturers of Improved Cast Steel Engineer- ingand Machine Files; , 5 ocornotive Engine, Railway Carriage and Wagon ‘pin 8. ., _ .. .. _, . guvvgs of every description, Engineers, Hammers, etc., etc., etc. i p , An assortmentef Steel from the above Works con- stantly on ‘hand by RICHARD’ MAKIN, ’ Agent for the Manufacturers, 43tf 65 Broad, strret. Huger, '1‘. P. 1 Northeastern Railroad, Charleston, S. C.