March 25, 1875] 



NATURE 



411 



the direction of the centrifugal force of the wave motion 

 according to the generally received theory. This force is 

 upwards at the crests, downwards in the hollows, and 

 horizontal midway betv/een the crests and hollows. If 

 the weighted arm is compelled to assume successive 

 angular positions, so that it is always at right angles to 

 the force, it is evident that the force will be continually 

 acting to cause the arm to rotate. It is easy to see how 

 the work is taken out of the waves, for when the vessel is 

 descending, the weight is performing the upper half of its 

 revolution, and is consequently exerting an upward cen- 

 trifugal force ; and when the vessel is ascending, the 

 centrifugal force is pushing down and resisting the vessel's 

 ascent, so that the revolving weight affords a resistance 

 against which the vessel can push just as if it were a 

 fixed point in space. The shaft of the revolving weight 

 can be made to turn a screw in the stern of the vessel by 

 means of a proper system of gearing, and by a delicate 

 arrangement of electric brakes and hydraulic accumu- 

 lators, Mr. Tower proposes to regulate the revolving arm 

 so as always to keep it at right angles to the centrifugal 

 force of the waves. 



THE FARAD A Y LECTURE 



LAST Thursday, as our readers know, Dr. A. W. 

 Hofmann, of Berlin, delivered at the Royal In<!ti- 

 tution the Faraday Lecture of the Chemical Society, his 

 subject being " Liebig's Contributions to Experimental 

 Chemistry." The audience included the Prince of Wales. 

 Dr. Odling occupied the chair. The dinner on Friday at 

 Willis's Rooms was probably one of the most remarkable 

 scientific dinners that have taken place for some years, 

 there being about 180 present, nearly all of them well- 

 known men of science. Dr. Hofmann made a noble 

 appeal on behalf of the recognition of the high value of 

 pure scientific research ; and Prof Huxley acknowledged 

 ha while in scientific ideas we might be abreast of the 

 Germans, yet the latter undoubtedly excelled us in the 

 amount of their scientific work. 



Dr. Hofmann in his lecture began by pointing out 

 that Faraday belonged by the universality of his genius 

 to all civiUsed countries, and the council of the Chemi- 

 cal Society had ordained that all countries should 

 be asked to join in rendering homage to the greatest 

 experimental thinker among mankind. On the pre- 

 sent occasion Germany had been invited to take part 

 in this international tribute, and it was a great honour 

 for him to interpret his country's homage. His illus- 

 trious teacher and lamented friend Justus von Liebig was 

 a master mind like Faraday, and Liebig's is the name 

 and figure alone fitted to stand on equal terms beside 

 Faraday. But to speak of Liebig only we must pro- 

 claim him one of the greatest contributors to chemistry 

 at large, while of organic chemistry he was the founder. 

 It is not only by the discovery of new facts that he 

 was distinguished, but by the conception of general laws 

 which illustrate both organic and inorganic chemistry. 

 By the great types of composition which under the name 

 of " radicles " he first spoke of, and by the researches to 

 which these led, he guided not only his contemporaries, 

 but will guide succeeding ages. He was also the first to 

 found in Europe the great system of practical education. 

 It was at Giessen he organised the first great laboratory 

 of experimental instruction ; and if we now admire mag- 

 nificent temples of science, let us not forget that we owe 

 them to him as their originator. He called around him 

 distinguished students, many of whom were raised now to 

 exalted positions by their talents and learning, and many 

 of whom the lecturer saw before him ; they would not 

 be wanting in the tribute of heartfelt reverence to their 

 great master. By his keen insight into chemical analogy 

 he marked out the way of chemical research, and he also 



showed how to keep up the supply of human hearts and 

 minds to prosecute his work. He provided arms, and 

 soldiers to wield them. 



There is no greater proof of the fecundity of genius than 

 that it enriches the storehouse of science with its disco- 

 veries, and at the same time provides the means of ulterior 

 conquest in ages yet to come. Which of us returning to- 

 morrow to his lonely post in the laboratory could not feel 

 cheered by the example of such men as Liebig and 

 Faraday? It was the habit of Liebig to trace laws in 

 their furthest results, and their applicability to promoting 

 the practical welfare of mankind. No one has in this 

 way more enriched us. Liebig's labours in abstract 

 science boie fruit in the useful arts. He materially eluci- 

 dated great industries, the manufacture of fulminating 

 compounds and prussiate of potash, for instance, together 

 with materials of the most important use in the manufac- 

 ture of the precious metals, and silver-coated mirrors, so 

 preferable for purposes of science and adornment to the 

 old mercury- backed glasses. Illustrans cemmoda vitac, he 

 never let slip any occasion of promoting the good of his 

 fellow-creatures. His penetrating philosophy could not 

 remain a stranger to the profound secrets of life based 

 upon chemical change. He revealed the dependence of 

 plants upon the chemical composition of the soil and air. 

 He studied also the laws of nutrition and development of 

 the animal body. In the former of these branches he 

 was crowned with the greatest success. He began in 

 1840 by his work on agriculture and zoology, written in 

 compliance with the request of the British Association at 

 their 1837 meeting at Liverpool, and he followed it up by 

 his work on husbandry. H is labours resulted in the estab- 

 lishment of the philosophy of agricultur-, and ranked him 

 with Lavoisier, who showed in the last century how the 

 vegetable stands between the mineral and the animal, 

 and collects from the former world food for the latter. 

 Lavoisier was followed by Humphry Davy, and after 

 him came Liebig. They are the three great lawgivers of 

 modem agriculture. 



It was in 1842 that Liebig, passing onward from food- 

 producers to animals, brought out his work on the sub- 

 ject, and it may be taken as a result of his work that the 

 superabundant animal food of thinly-peopled parts of the 

 earth has been, by a fast developing industry, brought 

 over to guard Europe against the pinch of want. Those 

 who are engaged in the curative art must bear him grati- 

 tude for the aiscovery of chloroform ; nor will they forget 

 chloral, the benign influences of which will even induce 

 sleep, and rank it among the most sublime agencies 

 placed at the disposal of therapeutics by chemical art. 



He had, the lecturer said, selected but a few illustrations, 

 which would give them a better idea than any long explana- 

 tions by him of Liebig's voluminous hfe-work, and he asked 

 them to accompany him in a rapid view of Liebig's memo- 

 rable contributions to chemistry proper. But Liebig's con- 

 tributions to the Royal Society's library were, in 1863,317 

 in number, and 283 were entirely by himself. When the 

 lecturer's pupils in Berlin heard that he had been en- 

 trusted with this lecture, they produced all the substances 

 which Liebig at any period of his career more particularly 

 illustrated ; these preparations now crowded the table. 



The first achievement he would allude to was that 

 which, whether or not his most brilliant discovery, con- 

 tributed most to facilitate the labours of chemists, and 

 was the main source of the marvellous development of 

 organic chemistry— analysis by combustion of organic 

 bodies and the determination of their carbon by his form 

 of measurement. Not one there but had determined the 

 molecular weight of bodies, but they might not be aware 

 that we are indebted for the process to Liebig. He never 

 published any particular paper on the subject, but merely 

 communicated his method in a paper on another che- 

 mist's researches. Its merit is simplicity, like that of his 

 air analysis. That an alkaline solution of pyrogenic acid 



