Seguin, in France, about the same time, invented the tubes which run through the locomotive boiler, and afford a passage to the flames. They greatly increased the evaporating surface, and consequently the production of steam. Stephenson discharged into the chimney the steam which had acted upon the piston, and thus gave a great draft to the furnaces. The locomotive was then complete, and since that day it has only been improved in its details.
We have wandered a little from the search for coal to speak of the steam engine, the locomotive, and the railway.
Many coal mines have been discovered by borings in search of artesian springs. About thirty years ago, in one of the French provinces, a well was being bored, and, quite unexpectedly, the boring tools revealed the presence of coal. As soon as this became known, everybody went to work searching, not for water, but for coal. In a region sixty miles long by twelve or fifteen wide, the ground was perforated like a sieve, by a series of borings which were laid down on a plan that seemed to resemble a constellation of stars on a celestial map. Everywhere coal was found, and altogether one hundred thousand acres of coal fields were added to the wealth of France. Nearly thirty companies were organized to work the new mines. Since the discovery about fifty pits have been sunk, some of them to a depth of five hundred yards. In 1851 the mines produced five thousand tons of coal. At the present day their product is not far from twenty millions of tons. All this originated in a search for water.
The process of boring for coal is very much like, in fact almost identical with, boring for petroleum. The boring rods are of wood, or iron, and are screwed together as the work proceeds. The primitive instrument is a steel chisel, or bit, which strikes the rock and wears it away, precisely as an ordinary drill makes a hole in a stone ledge. Boring machinery may be operated by steam power or by hand. In the primitive way, a triangle, or pair of shears, supports the rods, and has an ordinary windlass, by which they may be raised or lowered.
One of the inconveniences attending the ordinary process of boring is, that the rock is pulverized, and nothing but little fragments of dust and mud are brought to the surface. Sometimes it is difficult to determine whether the stones through which the borer has passed are the proper ones to indicate the existence of coal, or whether the black matter comes from coal or shales. All these disadvantages have been overcome by means of a new instrument, which is in general use. A gouge in the form of a hollow cylinder is employed, furnished at the base with a row of teeth, or with several cutting blades of cast steel, and sometimes with a row of diamonds. It is worked like an ordinary borer or auger, and cuts a solid column or cylinder out of the rock as regular in shape as if it had been turned in a lathe.