BOOK NOTICES. 57 



of masonry had to De sunk to the bed rock of the river, the magnitude of this un- 

 dertaking, upon which the ultimate success of the entire work depended, will at 

 once appear. The deepest of the piers went down no feet below the surface of 

 the water and of this distance more than two-thirds was below the bottom of the 

 river. Caissons of iron were used in sinking the piers, and the weight of the 

 masonry furnished the pressure for sinking the caissons. The special peculiarities 

 consist of the magnitude of the masses of material handled and the number of 

 special devices which the needs of the moment only could suggest. It does not 

 seem probable that any large bridge will in future be built upon piers before its 

 engineer has carefully studied the methods employed in sinking the piers of the 

 St. Louis bridge, and for this reason the value of the chapters devoted to this 

 subject cannot at present be fully estimated. 



The sinking of the piers afforded exceptional opportunities not easily repro- 

 duced for the study of the " Physiological effects of Compressed Air." Under this 

 title Prof. Woodward gives a resume of the experiences of the men who were em- 

 ployed in in the caisson and an exhaustive discussion of the subject from a scien- 

 tific standpoint. The explanations here given of phenomena, no doubt observed 

 before, are, so far as we know, quite new and have been endorsed by some of the 

 best physicians in the country. 



The special features in the manufacture of materials for the superstructure of 

 the bridge will be well shown by the following quotation from the book itself: 



" No sooner were preparations made for the construction of the arches than 

 practical difficulties appeared. It is true many of them had been anticipated, 

 but it is equally true that the difficulties actually met surpassed the shrewdest 

 conjecture. The steel makers found that their facilities were inadequate to the 

 magnitude of the work undertaken; their workmen were unskilled; and their 

 foremen without experience in working steel in such large masses. 



"Both iron and steel makers were unaccustomed to the rigid tests required. 

 The insertion into specifications of the items of elastic limit and modulus of elas- 

 ticity was a new feature in bridge contracts. Moreover, the detail drawings and 

 specifications indicated a grade of workmanship altogether exceptional. To be 

 sure they involved nothing, as regarded accuracy, either impossible or even diffi- 

 cult, but they were unusual and of course expensive. All these things now add 

 to the value and fame of the great work; without them this bridge would be 

 merely one of a thousand bridges, and this history never would have been writ- 

 ten ; but in 1871, '72 and '73, the fame of the bridge had little weight with a 

 contractor or with a stockholder. 



" Most of the real difficulties were actually overcome ; and through the influ- 

 ence of Mr, Eads's specifications the standard of good workmanship was raised 

 throughout the world, • In the construction of the St, Louis bridge, engineering 

 made progress. Let me quote on this point from so eminent an authority as 

 London Engineering: In its issue of October 10, 1873, the editor said: 'Our 

 present requirement being to select some example of the most highly developed 

 type of bridge-building of the present day, we have no difi&culty in passing be. 



