Cheyalier.] 284 (Jan. 4, 
The work of exploration during the year 1876 was much more extensive 
than that of 1875, and consisted as follows : 
First, In the study of the coasts bordering the sea, both in France and 
in England, and upon which each stratum of the material which consti- 
tutes them is easily distinguishable. This study of the coast naturally in- 
volved the geological examination of a zone more or less extended of the 
shore itself. 
Secondly, In a study of the bottom of the Channel so thorough as to 
enable us to draw a geological chart almost as exact as if the water had re- 
tired and its bed were left perfectly dry. This study was pursued by 
means of multiplied soundings in the sea, each one of which is marked 
upon the large map annexed to the reports which you have before you. It 
was proposed to conduct these operations in such a manner that the instru- 
ment at each sounding, beside indicating the depth of the water, should 
bring to the surface a sample of the rock forming the bottom of the sea. All 
these depths obtained, varying with the tide, have been modified by calcu- 
lation so as to be reckoned with reference to a uniform level. 
Finally, We have constructed on the shore at Sangatte, a shaft which has 
been sunk to the depth of 130 metres ; that is to say about twenty metres 
below the well-known clay subsoil which plays an important part in the 
geology of this region. Upon this clay lies the whole of the stratum compos- 
ing what geologists call the cretaceous formation, and which interests us 
particularly. Being impermeable, this bed of clay secures the lower layers 
of chalk from any uprising of the waters which are to be found on a still 
lower level. It is designated in the reports by the English name Gault. 
Of the three operations just enumerated, which have all been brought to 
a successful termination, the second, to wit, the study of the Channel with 
the design not only of making a hydrographical examination, but of draw- 
ing a geological chart of the bed of the sea, was the most delicate and the 
most complex. 
We do not hesitate to assure you, gentlemen, that this portion of the 
work of 1876 has been accomplished in a very superior manner. We do not 
believe that a work of hydrography and geology combined has ever been 
executed, carrying with it such certainty of result. These are merits which 
the authors of the reports, who were also the authors of the studies pur- 
sued, have not in any way sought to bring to notice, but to which we re- 
gard it our duty to call your attention. 
These divers explorations were organized and directed by the delegated 
member, Mr. Lavalley, who was enabled upon this occasion to show to what 
extent he is familiar with all the problems, however great or small, which 
may present themselves in public works. It is to him particularly that we 
owe the definite shape of the instruments designed for the deep sea souna- 
ings, which have proved so efficacious. To him also are we indebted for 
the ingenious arrangements that enabled us in the season of 1876 to accom- 
plish with perfect exactness and great rapidity the extraordinary number 
of soundings which we deemed indispensible in order to render ourselves 
