220 



KNOWLEDGE 



[OCTOBBE 2, 1899. 



tion into fact of the purely intellectual efforts of Lavoisier 

 and Priestley, of Galvani and Tolta, of Hutton and of 

 Cuvier. 



Sir Michael said "the Association has seen pass away 

 the men who, wise in their generation, met at York on 

 September 27th, 1831, to found it ; it has seen other great 

 men who in bygone years served it as presidents, or other- 

 ■wise helped it on, sink one after another into the grave. 

 Each year, indeed, when it plants its flag as a signal of 

 its yearly meeting, that flag floats half-mast high in token 

 of the great losses which the passing year has brought. 

 This year is no exception ; the losses, indeed, are perhaps 

 unwontedly heavy. 



The eyes of the young look ever forward; they take 

 little heed of the short though ever-lengthening fragment 

 of life which lies behind them ; they are wholly bent on 

 that which is to come. The eyes of the aged turn wist- 

 fully again and again to the past ; as the old glide down 

 the inevitable slope their present becomes a living over 

 again the life which has gone before, and the future takes 

 on the shape of a brief lengthening of the past. They who 

 study the phenomena of living beings tell us that light is 

 the great stimulus of life, and that the fulness of the life 

 of a being or of any of its members may be measured by 

 the variety, the swiftness, and the certainty of the means 

 by which it is in touch with its surroundings. I do not 

 propose to weary you by what in my hands would be the rash 

 efl'ort of attempting a survey of all the scientific results of 

 the nineteenth century. It will be enough if for a little 

 while I dwell on some few of the salient features dis- 

 tinguishing the way in which we nowadays look upon, and 

 during the coming week shall speak of, the works of Nature 

 around us — though those works themselves, save for the 

 slight shifting involved in a secular change, remain exactly 

 the same — from the way in which they were looked upon 

 and might have been spoken of at a gathering of 

 philosophers at Dover in 1799. And I ask your leave to 

 do so. 



In the philosophy of the ancients, earth, fire, air, and 

 water were called " the elements." It was thought, and 

 rightly thought, that a knowledge of them and of their 

 attributes was a necessary basis of a knowledge of the 

 ways of Nature. Translated into modern language, a 

 knowledge of these " elements ' of old means a knowledge 

 of the composition of the atmosphere, of water, and of all 

 the other things which we call matter, as well as a know- 

 ledge of the general properties of gases, liquids, and solids, 

 and of the nature and effects of combustion. Of all these 

 things our knowledge to-day is large and exact, and though 

 ever enlarging, in some respects complete. When did that 

 knowledge begin to become exact '? Let me ask you to 

 picture to yourselves what confusion there would be 

 to-morrow, not only in the discussions at the sectional 

 meetings of our Association, but in the world at large, if 

 it should happen that in the coming night some destroying 

 touch should wither up certain tender structures in all our 

 brains, and wipe out from our memories all traces of 

 the ideas which cluster in our minds around the verbal 

 tokens, oxygen and oxidation. How could any of us, not 

 the so-called man of science alone, but even the man of 

 business and the man of pleasure, go about his ways 

 lacking those ideas '? Yet those ideas were in 1799 lacking 

 ' to all but a few. Although in the third quarter of the 

 seventeenth century the light of truth about oxidation and 

 combustion had flashed out in the writings of John Mayow, 

 it came as a flash only, and died away as soon as it had 

 come. For the rest of that century, and for the greater 

 part of the next, philosophers stumbled about Ln darkness, 

 misled for the most of the time by the phantom conception 



which they called phlogiston. It was not until the end of 

 the third quarter of the eighteenth century that the new 

 light — which has burned steadily ever since — lit up the 

 minds of the men of science. The light came at nearly 

 the same time from England and from France. Bounding 

 off the sharp corners of controversy, and joining, as we 

 may fitly do to-day, the two countries as twin bearers of a 

 common crown, we may say that we owe the truth to 

 Cavendish, to Lavoisier, and Priestley. If it was Priestley 

 who was the first to demonstrate the existence of what we 

 now call oxygen, it is to Lavoisier we owe the true concep- 

 tion of the nature of oxidation and the clear exposition of 

 the full meaning of Priestley's discovery, while the know- 

 ledge of the composition of water, the necessary com- 

 plement of the knowledge of oxygen, came to us through 

 Cavendish and, we may perhaps add, through Watt. The 

 date of Priestley's discovery of oxygen is 1774. Lavoisier's 

 classic memoir " on the nature of the principle which enters 

 into combination with metals during calcination " appeared 

 in 1775, and (.'avendish'.s paper on the composition of 

 water did not see the light until 1784. During the last 

 quarter of the eighteenth century this new idea of oxygen 

 and oxidation was struggling into existence. How new 

 was the idea is illustrated by the fact that Lavoisier him- 

 self at first spoke of that which he was afterwards — namely, 

 in 1778 — led to call oxygen, the name by which it has 

 since been known, as " the principle which enters into 

 combination." What difficulties its acceptance met with 

 is illustrated by the fact that Priestley himself refused to 

 the end of his life to grasp the true bearings of the dis- 

 covery which he had made. In the year 1799, the know- 

 ledge of oxygen, of the nature of water and of air, and, 

 indeed, the true conception of chemical composition and 

 chemical change was hardly more than beginning to be, 

 and the century had to pass wholly away before the next 

 great chemical idea, which we know by the name of the 

 atomic theory of John Dalton, was made known. 



If there be one word of science which is writ large on 

 the life of the present time, it is the word " electricity " ; 

 it is, I take it, writ larger than any other word. The 

 knowledge which it denotes has carried its practical results 

 far and wide into our daily life, while the theoretical con- 

 ceptions which it signifies pierce deep into the nature of 

 things. At what time did this bright child of the nine- 

 teenth century have its birth ? He who listened to the 

 small group of philosophers of Dover, who in 1799 might 

 have discoursed of natural knowledge, would perhaps have 

 heard much of electric machines, of electric sparks, of the 

 electric fluid, and even of positive and negative electricity; 

 for frictional electricity had long been known and even 

 carefully studied. Probably one or more of the group, 

 dwelling on the observations which Galvani, an Italian, 

 had make known some twenty years before, developed 

 views on the connection of electricity with the phenomena 

 of living bodies. Possibly one of them was exciting the 

 rest by telling how he had just heard that a professor at 

 Pavia, one Volta, had discovered that electricity could be 

 produced not only by rubbing together particular bodies, 

 but by the simple contact of two metals, and had thereby 

 explained Galvani's remarkable results. For, indeed, as 

 we shall hear from Professor Fleming, it was in that very 

 year, 1799, that electricity as we now know it took its birth. 

 It was then that Volta brought to light the apparently 

 simple truths out of which so much has sprung. And 

 even Voltas discovery might have long remained relatively 

 barren had it been left to itself. When, however, in l.sl9, 

 Oersted made known his remarkable observations on the 

 relations of electricity to magnetism, he made the contact 

 needed for the flow of a new current of ideas. 



