addresses you would undoubtedly be a different man from what he is. His bone would have been different bone; his flesh different flesh—nay, the very gray matter of his brain, which is said to be concerned in the production of thought, would have been different from what it now is. I wrote to Mr. Norris from the Alps asking him to choose between a purely scientific lecture and an address based on the experiences of my own life. He chose the latter. I do not, however, ask you to blame Mr. Norris, but to blame me, if a chapter from the personal history of a worker, instead of proving a stimulus and an aid, should seem to you flat, stale, and unprofitable. . . . Speaking of the opportune beneficence of Dr. Birkbeck's movement reminds me that, in the days of my youth, personally and directly, I derived profit from that movement. In 1 842 and thereabout it was my privilege to be a member of the Preston Mechanics' Institution—to attend its lectures and make use of its library. One experiment made in these lectures I have never forgotten—Surgeon Corless, I think it was, who lectured on respiration, explaining, among other things, the changes produced by the passage of air through the lungs. What went in as free oxygen came out bound up in carbonic acid. To prove this he took a flask of lime-water, and, by means of a glass tube dipped into it, forced his breath through the water. The carbonic acid from the lungs seized upon the dissolved lime, converting it into carbonate of lime, which, being practically insoluble, was precipitated. All this was predicted beforehand by the lecturer, but the delight with which I saw his prediction fulfilled, by the conversion of the limpid lime-water into a turbid mixture of chalk and water, remains with me, as a memory, to the present hour. The students of the Birkbeck Institution may therefore grant me the honor of ranking myself among them as a fellow-student of a former generation. At the invitation of an officer of the Royal Engineers, who afterward became one of my most esteemed and intimate friends, I quitted school in 1839 to join a division of the Ordinance Survey. The profession of a civil engineer having then great attractions for me, I joined the survey, intending, if possible, to make myself master of all its operations, as a first step toward becoming a civil engineer. Draughtsmen were the best paid, and I became a draughtsman. But I habitually made incursions into the domains of the calculator and computer, and thus learned all their art. In due time the desire to make myself master of field operations caused me to apply for permission to go to the field. The permission was granted by my excellent friend General George Wynne, who then, as Lieutenant Wynne, observed and did all he could to promote my desire for improvement. Before returning to the office I had mastered all the mysteries of ordinary field-work, and by a fortunate opportunity, and with the sound knowledge of elementary geometry and trigonometry which I had acquired before leaving school, was enabled successfully to make some trigonometrical observations, though there had been bets against me. The pay upon the Ordinance Survey
