SIX LECTURES ON LIGHT

DELIVERED IN THE UNITED STATES

IN

1872-1873

BY

JOHN TYNDALL, D.C.L., LL,D., F.R.S.

LATE PROFESSOR OF NATURAL PHILOSOPHY IN THE ROYALINSTITUTION OF GREAT BRITAIN

London: Longmans & Co.

SIXTH IMPRESSION

LONGMANS, GREEN, AND CO.

39 PATERNOSTER ROW, LONDON

NEW YORK AND BOMBAY

1906

PREFACE TO THE FOURTH EDITION.

In these Lectures I have sought to render clear a difficult butprofoundly interesting subject. My aim has been not only todescribe and illustrate in a familiar manner the principal laws andphenomena of light, but to point out the origin, and show theapplication, of the theoretic conceptions which underlie and unitethe whole, and without which no real interpretation ispossible.

The Lectures, as stated on the title-page, were delivered in theUnited States in 1872-3. I still retain a vivid and gratefulremembrance of the cordiality with which they were received.

My scope and object are briefly indicated in the 'Summary andConclusion,' which, as recommended in a former edition, might be,not unfitly, read as an introduction to the volume.

J.T.

ALP LUSGEN: October 1885.

CONTENTS.