302 



NA TURE 



\Aiip;. 20, 1874 



ment of study, though Genius of course everywhere breaks 

 through these and other hindrances. The same circum- 

 stance has, on the other hand, maintained a closer con- 

 nection of the workers in science with all other classes of 

 the population, and incited to a more liberal care for the 

 instruction of the student not regularly trained. While 

 this has hitherto been quite rare in Germany, there have 

 long been in England solid and well-furnished insti- 

 tutions for the purpose. 



In the two circumstances, first that in England courses 

 of a moderate number of connected lectures can be de- 

 livered, and secondly that this can be done in buildings 

 well suited for demonstrations and experiments of every 

 kind, there is a great advantage over the general custom 

 in Germany, where each lectureronly delivers one lecture. 



Now, it is intelligible that during the seventy years 

 since this state of things has arisen, and under so 

 much more favourable external conditions, the English 

 public have educated their lecturers, and the lec- 

 turers their public, much better than has hitherto been 

 the case in Germany. The Royal Institution has had, 

 among its professors, two men of the first rank, Sir 

 Humphry Davy and Faraday, who have co-operated 

 to that end. At present Prof. Tyndall is held in 

 peculiarly high esteem, both in England and in the 

 United States, on account of his talent for popular 

 expositions of scientific subjects. Anyone who is conscious 

 within himself of the gift and the power of working in a 

 particular direction for the mental development of huma- 

 nity, has usually a pleasure in such activity, and is ready 

 to devote to it a good share of his time and his energies. 

 This is especially the case with Prof. Tyndall. He has, 

 therefore, remained true to his post at the Royal Institu- 

 tion, though other honourable posts have been offered 

 him. But it would be quite an erroneous conception to 

 think of him merely as the able, popular lecturer ; for the 

 greater part of his activity has always been given to 

 scientific investigation, and we owe to him a series of (in 

 part) highly original and remarkable researches and dis- 

 coveries in physics and physical chemistry. 



In his discourse On the scientific use of the Imagi- 

 nation, delivered before the British Association at Liver- 

 pool, Prof. Tyndall has given a peculiarly characteristic 

 description of his manner of intellectual working. There 

 are two ways of searching out the system of laws 

 in nature— that of abstract ideas, and that of thorough 

 experimental research. The former way leads ulti- 

 mately, through inathcmatical analysis, to an accurate 

 quantitative knowledge of the phenomena. But it can 

 only advance where the other has already, in some 

 measure, opened up the region, i.e. given an inductive 

 knowledge of the laws, at least, for tome groups of the 

 phenomena belonging to it, and the point is merely the 

 testing and clearing up of the already found laws, the 

 passage from them to the last and most general laws of 

 the region in question, and the complete unfolding of 

 their consequences. This other way leads to a rich know- 

 ledge of the behaviour of natural substances and forces, 

 in which at first the law-elenicnt is recognised only in the 

 form m which artists perceive it, through vivid sensuous 

 contemplation of tlie type of its action, in order to a later 

 working out of it in tlic pure form of an idea. These 

 two sides of the physicist's work arc never quite sepa- 



rate from each other, though sometimes the diversity of 

 individual gifts will adapt one man for mathematical de- 

 duction, another for the inductive activity of experimenta- 

 tion. Should the first method, however, become wholly 

 divorced from actual observations, it falls into the 

 danger of laboriously building castles in the air, on un- 

 stable foundations, and of not finding the points at which 

 it may verify the agreement of its deductions with fact. 

 The second, on the other hand, would lose sight of the 

 proper aim of science, if it did not work towards ulti- 

 mately bringing its observations into the precise form of 

 the idea. 



Tlie first discovery of laws of nature previously un- 

 known, that is, of new forms of likeness in the course of 

 apparently unconnected phenomena, is a matter of sense 

 (taking this word in its widest meaning), and must 

 nearly always be accomplished only by comparison of 

 numerous sensuous perceptions. The perfection and 

 purification of that which has been found falls alterwards 

 under the working of the deductive method of thinking, 

 and preferentially of mathematical analysis, as the final 

 question is ever about equality of quantities. 



Now Mr. Tyndall is par cxLclleiuc an experimenter ; 

 he forms his generalisations from extensive observations 

 of the play of natural forces, and carries over what he 

 has seen, in some cases to the greatest, in others to the 

 smallest relations of space (as appeared in the lecture re- 

 ferred to). It is quite a mistake to consider what he calls 

 imagination as mere fancy {Phaiitastcrci). It is exactly 

 the opposite that is meant — full sensuous contemplation. 

 To this mode of working is evidently to be attributed the 

 clearness of his lectures on physical phenomena, as also 

 his success as a popular lecturer. 



H. Helmholtz 



GROVE'S ''■ CORRELATION OF PHYSICAL 

 FORCES " 



The Correlation of Physical Forces. Sixth edition. With 

 other Contributions to Science. By the Hon. Sir W. R. 

 Grove, M.A., F.R.S., one of the judges of the Court of 

 Common Pleas. (London : Longmans, 1874). 



THERE are few instances in which anyone whose life 

 has not been exclusively scientific has made such valu- 

 able contributions to science as those of Sir W. R. Grove, 

 His nitric acid battery, to the invention of which he was 

 led, not by accident, but by a course of reasoning, which 

 in the year 1839 was as new as it was original, is a con- 

 tribution to science the value of which is proved by its 

 still surviving and continuing in daily use in every labora- 

 tory as the most powerful generator of electric currents, 

 while hundreds of batteries invented since that of Grove 

 have fallen into disuse, and become extinct in the struggle 

 for scientific existence. 



The gas battery, though not of such practical import' 

 ance, is still of great scientific interest, and the collection 

 which we have before us of those contributions to science 

 which took the form of papers, tempts us to indulge in 

 speculations as to the magnitude of the results which would 

 have accrued to science if so powerful a mind could have 

 been continuously directed with undivided energy towards 

 some of the great questions of physics. 



