The Montgomery advertiser., 1906-12-09

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 New York, Dec s.-(speciaI.) )-The sky scrapers are extending their inva- sion of lower Manhattan. and will soon be in possession of parts of Wall street. the financial centre of America. Heretofore the cloud piercing office buildings of the metropolis have been erected for the most part on lower Broadway. To be sure there are build ings on Wall street which tower to the height of ten or fifteen stories, but such structures are nor longer ranked as skscrapers in the metropolis Tn order to be classed as a skyscraper nowadays building must contain at least twenty stories above the pave ment. and then it is only one of the little brothers in the family of tall buildings. A forty story structure is in process of erection in this city, while the tower to be added to the Metro politan Life building. which occupies the site of Dr. Parkhurst's old church in Madison Square, will be 700 feet high. In other words. 1t will overtop the Washington Monument by 15O feet and will be about three-quarters the height of Eiffel tower.
 A modern office building often houses 4,000 persons. and the amount of daily business transacted in such structure is proved by d recent count of elevator traffic. which showed that in single building more than 6o,000 persons. number about equal to the 'entire population of Evansville, Ind, Portland, Me. or Oakland. Cal, Mad been transported up and down dur ing business hours. The Wall street skyscraper is to include twenty.fiye stories, and Is being built by the Trust Company of America, whose banking rooms will be the handsomest In New York.
 The work of putting up such a building is one which requires many months. even before the foundations reach the level of the street, and dur ing the past summer and fall the Trust Company of America's building has fur nished a striking illustration of the possibilities of modern construction methods It is an evidence of the coming of the era of concrete, the free use of which. together with the sys- tenn of caisson sinking, have lately wrought a revolutionary change in the builders art Fifteen years ago such a structure would have been an impossibility, no support strong enough to bear the weight having been devised at a time when piling was universally used in foundation work. It was in New York, in 1892, that for the first time in the world caissons were used to support the columns of a building. No foundation company at that time could think of any way to carry out the architects plan, so in desperation the architect turned to a bridge building firm and received from them an estimate well up into six fig ures. Today such a job Is far cheaper and is executed as a mere matter Of course.
 With the increase in the number of huge buildings the construction of loA a science in itself. Not only must the weight of the building be known, but also the character of the soil and rock beneath the building site. The foun- dation company, after getting the ar ohitects figures as to the weight Of the structure to be erected, turns to it's files and from them learns the probable conditions to be found when the excavations are made. The ability to gauge these conditions Is based on knowledge accumulated gradually as firms business increases. and 1t be- come a valuable stock in trade.
 Planting skyscrapers on Manhattan, however is a simpler task than simi- lar operations carried on in some oth- CT cities Here nature built upon a rock foundation, with a comparatively thin layer of soil for a covering, in consequence of which the work of sup porting a building, though arduous, IS not a difficult feat of engineering. In Chicago. on the other hand. where men could dig down indefinitely with out finding so much as a good sized boulder, the engineering architects were put to it to devise suitable sup ports for their skyscrapers- until some one thought out the now famous floating foundation" a sort of raft of steel and concrete built to bear tre- mendous weight. and floating upon the clay or gravel which takes the place of rock.
 To reach rock bottom in excavating for the Trust Company's building 1t was necessary to sink the foundations far below the tide-warer level. which was reached at a point about thirty feet below the curb At that level there was constructed. as the first step in sinking each caissons a working chamber for the "sand-hogs," or la borers, employed in the excavation This working chamber consisted Of box-like structure, minus top and bot tom, made of the stoutest timber ana cauIked to prevent water from enter