Nov. 20, 1 8 73 J 



NA TURE 



43 



whether the point proved is not that a glacial period has inter- 

 vened since the times of PaIa?olithic man and the present, rather 

 than tliat man existed in this country before the glacial epoch, I 

 think Mr. Tiddeman thinks as I do ; Init I take the liberty ol 

 stating this view more distinctly. O. Fisher 



Wave Motion 



In Nature, vol. viii. p. 506, Mr. Woodward has suggested a 

 simple and ingenious illustration of wave motion. Could he, or 

 any other correspondent, supply, or refer to, a popular expla- 

 nation of the action of the particles upon each other, to which 

 the propagation of the wave is due ? 



In the case of sound waves, the propagation is comparatively 

 simple, and is fully and clearly explained in Dr. Tyndall's " Lec- 

 tures on Sound," and elsewhere. Ilelmholtz, in his "Popular 

 Lectures," has figured the motion of the individual particle; of 

 which a water wave is composed. And in Sir John Herschel's 

 " Familiar Lectures," there is an elaborate and beautiful demon- 

 stration of the motion of the particles of ether in plane and cir- 

 cularly polarised light ; but neither of these expositions appears 

 to deal with the mode of propagation of the motion by which 

 the wave is formed. 



On the other hand, Sir Charles Wheatstone's ingenious model 

 beautifully exemplifies the interaction of zuaves and their results. 

 But here the waves are produced by the wooden wave forms 

 introduced into the machine, the beads representing the particles 

 remainmg fixed in relation to each other. Neither, therefore, 

 can this explain the manner and direction of the actual impact 

 of each particle upon the adjacent one (beginning with those in 

 contact with the source of motion itself), to which, combined 

 with the tendency to yield in the direction of least resistance, the 

 water wave must owe its form, and upon which the still more 

 complicated conception of the light wave must ultimately de- 

 pend. 



Could a reference be given to any practical explanation of this 

 point, it would confer a benefit on many who are not competent 

 to follow the subject into the higher mathematics. M. F. E. 



Sussex, Nov. 



Elementary Biology 



1, ALONG with many others, who are desirous of obtaining an 

 insight into Nature, would esteem it a great favour, and it would 

 be of the greatest benefit tons, if any of your scientific readers 

 would undertake to give through your columns a short account 

 of the various low forms of life included under the elementary 

 stage of biology of the Science and Art Department. They 

 might give instruction as to where the various objects could be 

 seen, how inspected, names of the best text-books for the 

 students' guidance, &c. 



By so doing, they would secure the praise of many who at 

 present cannot find out the modes of studying such subjects. 



Hull, Nov. S EiOLOGV 



Black Rain and Dew Ponds 

 CAn any of your readers explain the cause of this pheno- 

 menon ? On Thursday, the 4th Sept., about 5 P.M., in the village 

 of Marlsford, in the valley of the Thames, near Wallingford, a 

 heavy storm of rain occurred : and the water which fell in several , 

 parts of the village was found to be nearly black. It is described 

 as being of such a colour as would be produced by mixing ink 

 with water. Another of these black water showers fell during 

 the night of the following Friday. 



Would any reader of Naturk also kmdly set forth the theory 

 upon which the utility of the dew ponds, found in many of the 

 highest points of the Berkshire Downs, rests. They are circular 

 ponds made with considerable care, and are supposed to receive 

 so much dew as to supply all the water needed fjr the sheep in 

 their neighbourhood through the driest summer. 



Tiverton E. Highton 



ALBANY HANCOCK 



THE brief announcement by which some of our readers 

 may have first learnt of the decease of one of our 

 greatest biologists is, in its simplicity, in singular har- 

 mony with the life the close of which it commemorates. 



The retrospect of so serene a career leaves little to the 

 biographer, for its points seem marked rather by phases 

 of study, as indicated by important scientific memoirs, 

 than by incidents which the world regards as striking or 

 noteworthy. 



Albany Hancock was born at Newcastle-on-Tyne 

 on Christmas Eve, 1806. His father, Mr. John Han- 

 cock, died some six years later, and of the six little 

 children thus left dependent on their mother, Albany 

 was the third. He received a good education as times 

 then went, and on leaving school was articled to a 

 solicitor of good standing in Newcastle. Uncongenial 

 as was the employinent, he served his full term, passed 

 the customary examinations in London, and even 

 took an office in Newcastle with the view of esta- 

 blishing himself in practice. But the occupation was 

 irksome, and he gave it up ere long to join a manufactur- 

 ing firm, and this in turn circumstances led him soon to 

 abandon. The simple fact probably was that neither 

 occupation permitted him to follow the bent of his inclina- 

 tion, and that the desk and counting-house were alike dis- 

 tasteful to a mind pre-engaged as was his by other cur- 

 rents of thought. His early taste for natural history pur- 

 suits was probably in part derived from the collections, 

 chiefly conchological, formed by his father, who was in 

 many ways a man of superior ability, and had been some- 

 thing of a naturalist ; and association with the late Mr. 

 Robertson and Mr. Wingate, the one a botanist, the other 

 an ornithologist, of repute ; with the well-known Mr. Be- 

 wick ; and abova all with his near neighbour Mr. Alder, 

 confirmed his inclination in this direction. He was. as a 

 boy, clever with his finders, and that manual dexterity 

 which in later years served him so well when engaged 

 with dissecting needle and pencil, exhibited itself in many 

 of the pursuits of his early life. 



The first mention we find of Mr. Hancock's devotion to 

 natural history is in Mr. Alder's " Catalogue of Land and 

 Fresh-water shells," published in 1S30, in which the 

 author handsomely acknowledges the obligations he is 

 under to him and to Mr. John Thornhill "for the com- 

 munication of many habitats observed during their active 

 investigation of this as well as other branches of the 

 natural history of the neighbourhood " of Newcastle. His 

 earliest appearance as an author seems to have been in 

 connection with two short papers in the first volume of 

 " Jardine's Magazine of Zoology and Botany," published in 

 1836, the one a " Note on the Occurrence of Raniccps 

 trifurcatus on the Northumberland Coast," the other a 

 " Note on Falco riifipcs, Regiiliis ig?iicapiUus and Lams 

 minutus." These notices were, comparatively speaking, 

 of trifling significance, but they were the beginning of a 

 long series of contributions to knowledge which only 

 ceased when his last illness deprived him of the power of 

 continuous work. It is unnecessary here to enumerate 

 the successive memoirs that embody the results of his 

 life's labour. A catalogue of the original papers of which 

 he was author, or joint author, would extend to something 

 over seventy titles. 



Early association with Mr. Alder in the study of the 

 mollusca led to the production between the years 1845 

 and 1855 of their magnificent " Monograph of the British 

 Nudibranchiate Mollusca," which may still be taken as a 

 standard of excellence amongst such publications. Many 

 of Mr. Hancock's earlier papers were devoted to the elu- 

 cidation of the boring apparatus of the mollusca, and 

 these were followed by similar researches respecting the 

 excavating power of a group of sponges {Ciiona and allied 

 genera) which until that time had been but little known 

 or understood. 



As an anatomist— and after all it was his large know- 

 ledge of minute anatomy and infinite skill in dissection 

 that gave its especial value to most of his work — he was, 

 perhaps, best known by his elaborate memoir on the 

 Organisation of the Brachiopoda, published in the Philo- 



