April 30, 1885] 



NATURE 



617 



SOCIETIES AND ACADEMIES 

 London 

 Royal Society, April 16. — "Note on an Experiment by 

 Chladni." By Charles Tomlinson, F.R.S. 



Lord Rayleigh, in a memoir "On the Circulation nf Air in 

 Kundt's rubes, ' &c, remarks {Phil. Trans., 18S+, part 1, p. 1) 

 that "it was discovered by Savart that very fine powder does 

 not collect itself at the nodal lines, as does sand in the produc- 

 tion of Chladni's figures, but gathers itself into a cloud, which, 

 after hovering for a time, settles itself over the places of maxi- 

 mum vibration. 



In Savart's memoir, " Sur les Vibrations Normales" (An. de 

 C/i. et de Ph. for 1827, xxxvi. 1S7), the author distinctly claims 

 the above-named discovery. At p. 190 he refers to the nodal 

 lines of Chladni, but adds that by mixing with th; sand a finer 

 dust, such as lycopodium, "la poussiere fine se reunit pour 

 tracer d'autre lignes circulates que ce physicien n'a pas connues," 

 &c. 



Faraday, in his critical examination of Savart's memoir (Phi!. 

 Trans., 1S31, p. 299) apparently takes it for granted that 

 Savart started with an original observation. 



But this interesting discovery, which has been so fruitful in 

 beautiful results, is really due to Chladni. In his " Traite 

 d'Acoustique," Paris, 1S09, he remarks, p. 125 : — "Si un peu 

 de poussiere fine est melee au sable, elle pourra mieux servir 

 pour faire voir aussi les centres des vibration*, e'est-a-dire, les 

 endroits oil les parties vibrantes font les plus grandes excursions : 

 les molecules les plus petites de la poussiere s'accumuleront sur 

 ces endroits." 



Chladni is even more explicit in his " Neue Beytrage zur 

 Akustic" (4to, Leipzig, 1S17). At p. 7 he recommends " etwas 

 Pu/vis lycopodii " as the fine dust to be mixed with the sand ; 

 and at p. 69 he remarks that when fine dust accumulates on the 

 centres of vibration, it is in heaps more or less round or long, 

 &c. , according to the form assumed by the vibrating part. 



When Wheatstone reproduced Chladni's figuie< on square 

 plates (Phil. Trans., 1833, p. 593) he did not notice the re- 

 markable figures produced by mixing a fine powder with the 

 sand. This was the less necessary because Faraday's memoir 

 had been so recently published, and its conclusion was so satis- 

 factory, namely, that when a plate is vibrating, currents are 

 established in the air lying upon the surface of the plate, which 

 pass from the nodal lines towards the centres of maximum 

 vibration, and then, proceeding outwards from the plate to a 

 greater or less distance, return towards the nodal lines. 



With the exception of a very few elementary specimens on a 

 small scale, as given by Chladni and Faraday, this class of 

 figures has been neglected by writers on physics. The author 

 then gives directions for the production of these figures when 

 sand and lycopodium, flowers of sulphur, &c. , are used, and in 

 a folding sheet twenty-one are represented of plates of various 

 material and form. 



April 16. — "On the General Characters of Cymbulia." By 

 John D. Macdonald, R.N., M.D., F.R.S. 



The Pteropoda being so purely pelagic in their habit place- 

 them out of the reach of zoologists in general ; and even sys- 

 tematic writers, as in other cases, are often misguided by in- 

 correct figures and descriptions made up probably from scanty 

 or defective data, but which have, nevertheless, been handed 

 down to us with a show of truth. 



The author was impressed with the idea that the figures and 

 descriptions of the species of Cymbulia extant were not reliable ; 

 and having had an opportunity of examining some specimens 

 taken in the Indian Ocean, he found that such was really the 

 case. In the natural position of the animal the toe of the 

 hyaline slipper of Cymbulia should be taken as posterior, and 

 the broadly-notched heel as anterior. Both animal and shell 

 are reversed in Mr. Adams's figure of Cymbulia proboscidea, but 

 this is, after all, an error of less importance than that in De 

 Blainville's figure, in which, although the shell is represented 

 in its proper position, the animal is reversed. A pair of eyes 

 are also given in a position where ears alone would be possible, 

 while there is no more evidence of the existence of eyes in 

 Cymbulia than in any other genus of Pteropods. The notion 

 of a ventral connecting lobe between the fins is a mistake, 

 though these organs are connected above and behind so as to 

 form a broad, continuous plate. 



Zoological Society, April 21. — Prof. W. H. Flower, 

 LL.D., V.P.R.S., President, in the chair.— Mr. Sclater ex- 



hibited and remarked on a pair of pheasants from Bala 

 Murghab, Northern Afghanistan, belonging to H.R.IL the 

 Prince of Wales. — Mr. G. E. Dobson, F.R.S., exhibited some 

 skulls of Crocidura aranea, and pointed out that they possessed 

 supernumerary teeth (premolars) in the upper jaw. — The Secretary 

 exhibited, on behalf of M. George Claraz, an egg of Darwin's 

 Rhea ; and read some notes by M. Claraz on the habits and 

 distribution of this Rhea. — Mr. G. A. Boulenger exhibited a 

 specimen of a Brazilian Snake which bad partly swallowed an 

 Amphisbtenoid Lizard. The lizard had in its turn partly eaten 

 its way out through the body of the snake. — A communication 

 was read from Sir Richard Owen, K.C.B., containing re- 

 marl. * on the structure of the heart in Ornithorhynchus and in 

 Apteryx. — Mr. Oldfield Thomas read a paper on the characters 

 of the different forms of the Echidna of Australia, Tasmania, 

 and New Guinea, all of which he was inclined to refer to one 

 varying species. — Dr. St. George Mivart, F.R.S., read a memoir 

 on the anatomy, classification, and distribution of the Arctoidean 

 Carnivorous Mammals. The author, after briefly noticing the 

 papers of other naturalists who have of late years treated of this 

 subject, described the main facts concerning the anatomy of the 

 various Arctoid genera, especially as regards their osteology and 

 dentition, and gave detailed comparisons of the proportions of 

 the various parts of the skeleton, comparing them with those of 

 the .Eluroids and Cynoids.— Dr. F. H. II. Guillemard, F.Z.S., 

 read the second part of his report on the collection of birds 

 made during the voyage of the yacht Marchesa. The present 

 paper gave an account of the birds collected in Borneo. It also 

 contained notes on some birds obtained on the island of Cagayan 

 Sulu, on the north-east coast of Borneo. 



Royal Microscopical Society, April 8. — The Rev. Dr. 

 Dallinger, F.R.S., President, in the chair. — Mr. Crisp exhibited 

 a model of an old microscope described in an Italian work pub- 

 lished in 16S6. — Mr. II. G. Madan exhibited and described 

 Bertrand's polarising prism. He also exhibited a modification 

 of Ahren's double-image prism. — Mr. Dowdeswell exhibited 

 some septic microbes from high altitudes, and detailed experi- 

 ments as to bacterial germs found at various heights, notably 

 upon the Neisen, at an elevation of about 7500 feet. — Mr. 

 A. D. Michael gave a summary of his paper on " New British 

 Oribatidae." He first called attention to the nymph of Cepheus 

 bifidatus, which he had just discovered ; the species is very rare, 

 and the immature stages were not known. Last September, at 

 Keswick, Mr. Michael found two or three specimens, and 

 instead of preserving them as examples, determined to try and 

 breed from them. He isolated them, and after some weeks 

 obtained a few eggs, from which he reared four larva; ; these he 

 has carefully watched for six months until they had changed 

 to nymphs and become full grown ; he then killed and oreserved 

 two specimens of the hitherto unknown nymph, reserving the 

 two others to rear to the imaginal condition. One was lost just 

 before the final change, the other lived. The nymph which was 

 exhibited was a very remarkable and beautiful creature, sur- 

 rounded with concentric rows of curved serrated spines longer 

 thon the body. Mr. Michael then called attention to a new 

 species oi Hypochthonius, pioposed to be called //. lanatus. The 

 abdomen is segmented, and the segments are to a certain extent 

 retractile, as in many insects ; this enables the creature to erect 

 or lower the long spines attached to the edges of the segments at 

 will. — -An interesting new species, to be called Notaspis terrains, 

 abundantly provided with long serrated hairs, and a curious 

 nymph of a Damteus, to be called D. ttnupes, which carries its 

 cast dorsal skins in a pyramid on its back, like a pile of dish 

 covers, and has a central projection on each skin, forming a 

 column to support the whole, were also shown and described, 

 besides other new species. — Mr. Crisp called attention to some 

 very interesting experiments by Dr. Nussbaum and Dr. Gruber, 

 on the artificial division of infusoria. Dr. Nussbaum divided an 

 Oxytricha into two halves, either longitudinally or transversely, 

 and found the edges at the point of division were soon sur- 

 rounded with new cilia. Dr. Gruber artificially divided Stenter 

 caruleus with similar results. — Mr. C. H. Kain's letter on the 

 use of balsam of Tolu was read. — Mr. H. Mills's note on the 

 filamentous projections on the margin of the diatom (Stephano- 

 di.nis niagane) was read, and slides in illustration were exhibited. 

 — Mr. G. C. Karop remarked on an examination he had recently 

 made of the saliva in a case of hydrophobia. The specimens 

 presented the following characters . — Epithelium in large masses, 

 most of the cells crowded with micrococci ; bacilli of various 

 lengths, and very variable iu diameter. A few showed evidence 



