284 Wisconsin Academy of Sciences, Arts, and Letters. 



to rock if lateral motion is prevented. There is, however, one 

 precaution necessary, and this is, that the thickness of the bed of 

 sand and the substratum should be examined and verj carefully^ 

 as many cases have occurred in which the superstrata of sand was 

 not of sufficient thickness to give reliable resistance. In such 

 cases, as in the fifth class, resort to artificial support must be had 

 as will be noticed as I progress. 



In the 4th class there is no particular precaution necessary as it 

 is presupposed, as already stated, that the bed will give sufficient 

 resistance. 



In considering the sixth class we arrive at that portion of our 

 work where we may expect to meet the unusual difficulties, where 

 science is often at fault, and where extensive practical knowledge 

 is necessary to overcome the difficulty. It would perhaps be a 

 loss of time for me to go over the ordinary methods of construct- 

 ing foundations in what are considered substantial beds, excepting 

 where I may have occasion to touch upon foundations for partic- 

 ular structures, my purpose is to review the best methods of 

 overcoming the greatest difficulties. 



General Delafield, ex-Chief of the U. S. Engineer Corps, has 

 written a work upon foundations in yielding soil, in which he 

 gives conclusive proofs of failure, in every case, of grillage or 

 platform foundations. These foundations are made by excavating 

 to a sufficient depth and placing two or more courses of strong 

 timbers at right angles over the ground to be occupied ; the spaces 

 between the timber are then filled with beton composed of cement, 

 sand and broken stone or gravel. Over this is placed one or more 

 courses of strong plank placed in close position and securely fast- 

 ened to the grillage, and the structure is erected upon the floor 

 thus resulting. 



As before stated, these foundations have failed in every instance 

 where extensive permanent buildings have been erected upon the 

 same, and it was the opinion of General Delafield that the same 

 should not be used unless in connection with some more reliable 

 supports. 



The platform foundation being a failure, our next resort is piling, 

 and the different manners in which this may be applied, is one of 

 the particular points I wish to touch upon in this paper. 



