226 REPORT— 1876. 



may be employed, wholly or partly composed of clay tipped in front of tlie line of 

 fovmdations, a space for wliich has previously been dredged to the reqim-ed depth 

 •when necessary, or, in the event of clay not being within reach, an embankment 

 may be constructed composed of the local soil, faced with clay and coated with 

 stones in order to insure its stability. A water-tight dam is thus formed, and the 

 excavations for the foundations may be further protected by the insertion of piles, 

 either driven or screwed into the inner slope of the dam and also into the opposite 

 side of the cutting. The piles have vertical gi-ooves, into which a timber boarding 

 may be slipped, thus formmg a thoroughly dry box-dam in which foundations may 

 be built in situ ; or if no such box-dam be formed, the foundations may be sunk by 

 means of excavators. 



For the construction of bridge-piers in open water, the site may be dredged to 

 the required depth and clay deposited, so as to form an embankment rising above 

 water-level, down tlirough which an excavation is made and the foundations built, 

 or through which they may be simk; they may also be floated into position. 



To construct subways beneath water, the river-bed is dredged, and clay mixed 

 with ground chalk and cement deposited so as to form a water-tight roof to the 

 operations, and the subway may be formed by tunnelling through the body of the 

 clay, gi'ound chalk, and cement, if deposited in sufficient quantity. 



The foundations may be formed of masses of stone masonry, brickwork, or con- 

 crete, whose horizontal section consists of two members at right angles to one 

 another, these members being hollow, to permit of excavation being carried on in 

 their interior while being sunk. Tongues or grooves of a semicircular or other 

 shape are formed on the ends of one of the members, the other constituting a 

 counterfort. 



For the purpose of facilitating the sinking of foundations, the toe or bottom 

 should be surrounded with a shoe or curb. 



The author then described at length the drawings which were exhibited. 



In conclusion he stated, it is of the utmost importance that every facility should 

 be given to the free action of the ebb aud flow of a river, because an obstruction 

 weakens its action, thereby withdrawing a certain amount of force from its power. 

 The advantage of these walls is that they otter comparatively little resistance to 

 the water. 



Walls of this description might be faced with hard rubble-stone of from 3, 4, 5, 

 6, 8, and 10 cwt. each, the remainder of brickwork or concrete. Iloman cement or 

 hydraulic lime ground with mine-dust or puzzolano might be used with advantage 

 in the work if of rubble built in situ. 



When the deposition is of great depth, as in the Clyde, varying from W to 90 feet 

 in some places, the breadth of base cannot be overestimated, more particularly 

 where subject to great weights. From tliis construction a base of 32 feet or more 

 would be obtained, thereby giving great stability, also affording accommodation for 

 water-, gas-, and sewage-pipes. 



The alveus or channel of a river is subject to move upwards as well as sidewise, 

 from causes not always in the immediate vicinity but at a distance. 



On Reuleaiuvs Treatment of Mechanisms. By Prof. A. B. W. Kennedy. 



Importance of Hydro-Geolocjical Surveys from a Sanitary point of view. 

 By Baldwin LATHAir, C.E. 



The author in his paper pointed out that all subterranean stores of water were 

 due to the rainfall percolating into the earth, but that there were matters which 

 aftected the quantity of water percolating, such as the nature of the outcrop of the 

 strata receiving the rainfall, the volume of the strata, the lithological character, 

 and the free communication between different parts. The water held in store in 

 the earth did not, as a rule, maintain a horizontal level, but the surface possessed 

 a considerable fall in directions corresponding to the points of the discharge of the 

 springs. The inclined surface of the water pointed to its movement in the direc- 



i 



