The power of regulating the length of paper for each mile was of great importance; it enabled me to examine, almost microscopically, the junctions of the rails. When a large scale of paper was allowed, every joining was marked upon the paper.
I find, on referring to my paper records, that on the 3rd March, 1839, the “Atlas” engine drew my experimental carriage, with two other carriages attached behind it, from Maidenhead to Drayton, with its paper travelling only eleven feet for each mile of journey; whilst from Drayton to Slough, forty-four feet of paper passed under the pen during each mile of progress.
The inking pens at first gave me some trouble, but after successively discovering their various defects, and remedying {331} them at an expense of nearly £20, they performed their work satisfactorily. The information they gave might be fully relied upon.
〈THEIR REMARKABLE EFFECT.〉
We had an excellent illustration of this on one occasion when we were returning, late in the evening, from Maidenhead, after a hard day’s work. The pitchy darkness of the night, which prevented us from seeing any objects external to our carriage, was strongly contrasted with the bright light of four argand lamps within it. I was accompanied by my eldest son, Mr. Herschel Babbage, and three assistants. A roll of paper a thousand feet in length was slowly unwinding itself upon the long table extended before us, and winding itself up on a corresponding roller at its other extremity. About a dozen pens connected with a bridge crossing the middle of the table were each marking its own independent curve gradually or by jumps, as the circumstances attending our railway course was dictating. The self-feeding pens, which the self-acting roller of blotting-paper continually followed, but never overtook, were quietly marking their inevitable courses. All had gone on well for a considerable time amidst perfect silence, if the steady pace of thirty miles an hour, the dogged automatic action of the material, and the muteness of the living machinery, admitted of such a term. Being myself entirely ignorant of our position upon the rail, I disturbed this busy repose by inquiring whether any one knew where we were? To this question there was no reply. Each continued to watch in silence for the duties which his own department might at any moment require, but no such demands were made.
After some minutes, as I was watching the lengthening curves, I perceived a slight indication of our position on the railroad. I instantly looked at my son, and saw, by a faint {332} smile on his countenance, that he also perceived our situation on the line. I had scarcely glanced back at the growing curves upon the paper, to confirm my interpretation, when each of my three assistants at the same instant called out “Thames Junction.”
At the period I speak of the double line of a small railway, called the Thames Junction, crossed the Great Western line on a level at between two and three miles from its terminus. The interruption caused certain jerks in several of our curves, which, having once noticed, it was impossible to mistake.
I would suggest that every engine should carry a spring clock, marking small equal intervals of time by means of a needle-point impinging upon paper, the speed of whose transit should be regulated by the speed of the engine. It might, perhaps, be desirable to have a differently-formed mark to indicate each five minutes. Also, two or more studs on the driving-wheel should mark upon the same paper the number of its revolutions. Besides this, it might be imperative on the engine-driver to mark upon the paper a dot upon passing each of certain prescribed points upon the railway. This latter is not absolutely necessary, but may occasionally supply very valuable information.
〈TRACTIVE POWER REGISTERED.〉
The second point which I consider of importance is, that—