The water together with all the material washed up should be caught in a tub; the samples should be preserved in small bottles with identifying labels, the location of the holes be properly shown upon topographical plans and the material encountered at various depths in each hole be properly noted upon profiles or sections.
It is obvious that gravel or stones too large to be washed up between the drill rod and the casing will not be represented in the sample. The sample is also often deficient in that some of the finer material is usually not allowed to settle in the tub, but is lost in the overflow. Nothing short of preserving the entire effluent until the finest material had completely settled would entirely obviate this latter difficulty; even then the settled material would be a redistribution (through the process of settling through water) of the actual material encountered.
It has been attempted without much success to obtain a continuous (though of course inverted) sample; by diverting (through a hole in the bottom of the spout to the tub) a continuous certain per cent, of the effluent. The material thus diverted caught in a long narrow box constructed, for observation, with one glass side and having corresponding depths marked at intervals as the sample grows. After all much depends upon the honesty, experience and intelligence of the man directly in charge and upon the completeness of his notes. The "feel" of the drill rod, the color and amount of the effluent, whether or not the drill rod can be advanced beyond the casing, etc., are all instructive to the drill runner and to the man who interprets the results.
The most illuminating note that can be made is as to the amount of the effluent compared with the water supplied. If all the water is recovered it indicates an impervious material and the effluent will undoubtedly show considerable clay; on the other hand, if all the water is lost when the drill rod is advanced, and much of it even with the casing in advance, quite open sand or gravel is indicated, and the effluent will be correspondingly clear.
Boulders, unless very large, can be differentiated from ledge by the rebound and ring of the drill rod pounding on it because the ledge gives a more springy and ringing rebound. By driving the casing to whatever rock is encountered, and persisting with the drill rod, easily identified rock chips can almost always be obtained to assist in the diagnosis of boulder or ledge.
After the boring is finished the casing should be left in such holes as it is desired to extend down into rock by means of a diamond drill. In many cases it will be of value to observe the elevation and fluctuations of the ground water in the casing.