The Silk Trade of Lyons, France

1878 Scientific American  
A NEW MEANS TO PREVENT INCRUSTATIONS tance would be heard, which would be inaudible near the notable types of American iron bridges of large spans, the IN BOILERS. trumpet. Louisville bridge having among its 27 spans one span of 400 3. The arc of the horizon from which the echo appeared feet and one of 370 feet, and the St. Charles bridge having I A BIRMIN GHAM firm, Cooper & Smith, recommend for to come was also increased, in some cases, to more than four spans of 320 feet and three of 305
more » ... . In the Louis· t preventing the formation of incrustations in boilers two pre· three times that subtended by the echo at the place of the ville bridge the total weight of wrought and cast iron in the parations made by them, and consisting of tannate of sodium. trumpet. This fact again indicates that the echo consists of 400·foot span was 627 tons, and the total dead weight of the i They are put into the market as "crystallized tannate of multiple sounds from various points at or near the surface span, including its two overhanging side paths, was 743 . sodium " and" liquid tannate " respectively. The latter is a ; of the sea, the angle which the aggregate of these points tons, or 4,162 pounds per lineal foot. The bridge, in addi·; solution of tannic acid in one of carbonate of sodium, and subtend necessarily becoming greater as the steamer ad· tion to its own weight, was proportioned for a rolling load of' contains about 12 per cent. of tannin. The liquid has a vances. 2,600 pounds per lineal foot, and with this maximum load specific gravity of 1 ' 105, and is of a dark red color. The lat· But perhaps the most important facts in r€gard to the echo the factor of safety in the cast·iron braces is from five to six ter is probably caused by the o�iding action of the air on . are those derived from the series of observations made in reo by Hodgkinson's formula. The de.pth of truss of the 400-the tannin. The crystallized tannate has a similar composi· ' gard to it by Mr. Henry W. Clark, the intelligent keeper of foot span, which Col. Fink called" a modified triangular tion, containing less tannin, however. Both preparations are I the principal lighthouse station on Block Island, and by truss," was 46 feet, or less than one-ninth of the span; the easily soluble in water, and perfectly free from substances I Joseph Whaley, keeper of the Point Judith lighthouse. Mr. proportion in the wrought·iron trusses of the Cincinnati and which migllt rise with the steam and injure the machinery. Clark was furnished with a time· maker to observe the dura Louisville bridges, specially cited by Mr. Clarke, being one· They do not attack the boiler walls, and many of the owners I tion of the echo, and both were directed to sound the trum tenth of the span. Mr. Clarke's paper and the discussion of large factories have testified to the efficiency of those pre· pets every Monday morning for half an hour, noting the thereon would doubtless be read with special interest by parations as preventives of incrustations, and to their ten-temperature, the height of the barometer, the state of the railway engineers in India, where as yet only six bridges dency to loosen and destroy those when already formed. weather as to clearness or fog, the direction and intensity of have been erected, the spans of which exceed 180 feet. the wind, and the surface of the ocean. With the exception of the Bahowalpore bridge, the founda· From the observations made at these two points, for more tions of which are carried down to the depth of 100 feet, no AMERICAN ANTHRACITE COAL IN THE than two years at one station and over a year at the other, bridge in the Punjaub has greater spans than 142 feet, the MEDITERRANEAN. the echo may be considered as produced constantly under all precise length reckonmg from center to center of the piers conditions of weather, even during dense fogs, since at of each of the 64 wrought-iron trussed spans of the famous T HE follow i ng is taken from an Austr i an journa l : " The Block Island it was heard 106 times out of 113, and at Point bridge across the river Chenaub at Wuzerabad. fact that two cargoes of anthracite have been shipped to a Judith 50 times out of 57, and on the occasions when it was French port not long ago, calls our attention to a new field, not heard the wind was blowing a gale, make a noise suffi MR, SHALER SMITH ON THE BRIDGES OVER THE OHIO AN D, in which we shall have to meet American competition. The ciently intense to drown the sound of the echo. These reo KENTUCKY RIVERS.
doi:10.1038/scientificamerican12071878-2437esupp fatcat:vehxju727nfnjpbhzv4gtl7sha