42 



NATURE 



[May 12, 1 88 1 



Brooks, London International College ; silver medal, Chas. Th. 

 Knaus, Duhvich College. 



The Willem Barent!, the little Polar ship which has already 

 made three voyages to the Northern Polar Sea, has left 

 Amsterdam for ihe fourth time. The crew consists of a 

 lieutenant of the Royal Navy, H. van Broekhuyzen, as captain, 

 two other officers, a physician, a zoologist, a photographer (the 

 Englishman, Mr. Grant), and six sailors. 



Doctors Arthur and Aurel Krause have left Bremen 

 to spend some time in the neighbourhood of Behring Straits for 

 the purpose of exploring and collecting, at the expense of the 

 Bremen Geographical Society. They will visit the Chukchi 

 peninsula, Behring Islands, and Alaska, where they will make 

 zoological collections and carry on various scientific observations. 



Mr. Henry Soltau and Mr. J. W. Stevenson, of the China 

 Inland Mission, have successfully made the journey from Bhamo 

 into China, reaching I-chan-fu, on the Vang-tsze-kiang, on 

 March 14. This is the first time that it has been accompUshed 

 by Europeans, and the time occupied was about four months. 



The first paper in the May number of Feteriiiann' s Miltkeil- 

 ungcn is a study of the Padolian Dniester region hy Ritter v. 

 Habdank Dumkowski. This is followed by the continuation of 

 Dr. Radde's account of his journey to Talysb, Aderbeijan and 

 the Sawalan ; M. Charr.ay's expedition to Central America 

 from the North Amcruan Review ; M. Potanin's researches in 

 Western Mongolia in 1876-77, with a map; Recent Surveys in 

 the Western Onited States, with a map ; and the usual Monthly 

 Notes. Among the latter is a long account of Dr. Lenz's journey 

 to Timbuctoo, with a sketch-map. 



We have received Nos. i and 3 of the Bulletin of the 

 American Geographical Society, the two most important pajers 

 in which are on the recent investigations of the Gulf Stream, by 

 the U.S. Coast Survey steamer Blake, by Commander J. R. 

 Bartlett, and Changes in the Physical Geography of the Ancient 

 Home of Man in Central ai.d Western Asia, by the Rev. Owen 

 Street. 



Dr. Moffat, the venerable missionary and pioneer explorer 

 in Africa, was entertained at a banquet in the Mansion House 

 on Saturday. 



The Bulletin of the Society of Commercial Geography of 

 Bordeaux contains a brief statement of M. Paul Soleillet's 

 views on the African question. After addressing the Society 

 M. Soleillet proceeded to Paris, but he entertains hopes of 

 being able to return to West Africa in November. 



THE PRODUCTION OF SOUND BY RADIANT 



ENERGY^ 

 JNmy Boston paper en the photophone (Nature, vol. xxii. 

 p. 500) the discovery was announced that thin disks of very 

 many ditferent substances emitted sounds when exposed to the 

 action of a rapidlyinttnupted beam of sunlight. The great 

 variety of material used in these experiments led me to believe 

 that sonorousness under such circumstances would be found to 

 be a general property of all matter. 



At that time we had failed to obtain audible effects from 

 masses of the various substances which became .'onorous in the 

 condition of thin diaphragms, but this failure was explained 

 upon the supposition that the molecular disturbance produced 

 by the light was chiefly a surface action, and that under the 

 circumstances of the experiments the vibration had to be trans- 

 mitted through the mass of the substance in order to affect the 

 ear. It \a as therefore supposed that if we could lead to the ear 

 air that was directly in contact with the illuminated surface, 

 lender sounds might be obtained, and solid masses be found to 

 be as .'onorous as thin diaphr.agms. The first exi eriments made 

 to verify this hypothesis pointed towards success. A beam of 

 sunlight was focussed into one end of an open tube, the ear 

 being placed at the other end. Upon in'errupting the beam, a 

 clear musical tone was heard, the pitch of which depended upon 

 the frequency of the interruption of the light and the loudness 

 upon ihe material composing the tube. 



While in Paris a new form of the experiment occurred to my 

 mind, which would not only enable us to investigate the sounds 

 produced by mass es, but would also permit us to test the more 



' Abstract of a p.iper bv Prof. .Alexander Graliam Bell, read betore the 

 National Academy of Arts and .Sciences, April 21, 18S1. 



general proposition that sonorousness, under the influence of 

 intermittent light, is a property common to all matter. The 

 substance to be tested was to be placed in the interior of a 

 transparent vessel made of some material which (like glass) is 

 transparent to light but practically opaque to sound. 



Under such circumstances the light could get in, but the 

 sound produced by the vibration of the substance could not get 

 out. The audible effects could be studie4 by placing the ear in 

 communication with the interior of the vessel by means of a 

 hearing tube. 



Some preliminary experiments were made in Paris to test this 

 idea, and the results were so promising that they were communi- 

 cated to the French Academy on P6tober 11, 1880, in a note 

 read for me by Mr. Antoine Breguet. 



I wrote to Mr. Tainter suggesting certain experiments, and upon 

 my return to Washington in the early part of January, Mr. 

 Tainter communicated to me the results of the experiments he 

 had made in my lal.oratory during my absence in Europe. He 

 had commenced by examining the sonorous properties of a vast 

 number of su' stances inclosed in test-tubes in a simple empirical 

 search for loud effects. He was thus led gradually to the 

 discovery that cctton-wool, worsted, sill-, and fibrous materials 

 generally, produced much louder sounds than hard rigid bodies 

 like crystals, or diaphragms such as we had hitherto used. 



In order to study the effects under better circumstances he 

 inclosed his materials in a conical cavity in a piece of brass 

 closed by a flat plate of glass. A brass tube leading into the 

 cavity served for connection with the hearing-tube. When this 

 conical cavity was stuffed with worsted or other fibrous materials 

 the sounds produced w ere much louder than when a test-tube 

 was employed. Mr. Tainter next collected silks and worsteds of 

 different colours, and speedily found that the darkest shades 

 produced the be-t effects. Black worsted especially gave an 

 extremely loud sound. 



About a teaspoonful of lamp-black was placed in a test-tube 

 and exposed to dn intermittent beam of sun-light. The sound 

 produced was much louder than any heard before. Upon 

 smoking a piece of plate-glas":, and holding it in the intermittent 

 beam with the lamp-black surface towards the sun, the sound 

 produced was loud enough to be heard, v\ith attention, in any 

 ]3art of the room. With the lamp-black surface turned from 

 the sun the sound was much feebler. 



Upon smoking the interior of the conical cavity and then 

 exposing it to the intermittent beam with the glass lid in position 

 as shown, the effect was perfectly startling'. The sound was so 

 loud as to be actually painful to an ear placed clo: ely against the 

 end of the hearing-tube. The sounds, however, were sensibly 

 louder when we placed some smoked wire gauze in the receiver. 

 When the beam was thrown into a resonator, the interior of 

 which had been smoked over a lamp, most curious alternations 

 of sound ar.d silence were observed. The interrupting disk was 

 set rotating at a high rate of speed, and was then allow-ed to 

 come gradually to rest. An extremely feeble musical tone was 

 at fir.st heard, which gradually fell in pitoh as the rate of inter- 

 ruption grew less. The loudness of the sound produced varied 

 in the most interesting manner. Minor reinforcements were 

 constantly occurring, which became more and more marked as 

 the true pitch of the resonator was neared. When at last the 

 frequency of interruption corresponded to the frequency of the 

 fundamental of the resonator, the sound produced w as so loud 

 that it might have been heard by an audience of hundreds of 

 people. 



The extremely loud sounds produced from lamp-black have 

 enabled us to demon-trate the feasibility of using this substance 

 in an articulating photophone in place of the electrical receiver 

 formerly employed. Words and sentences spoken into the 

 transmitter in a low tone of voice were audibly reproduced by 

 the lainp-black receiver at forty metres distance. 



In regard to the sensitive materials that can be employed, our 

 experiments indicate that in the case of solids the physical con 

 dition and the colour are tw-o conditions that markedly influence 

 the intensity of the sonorous effects. The loudest sounds are 

 pre duced from substances in a loose, porous, spongy condition, 

 and from those that have the darkest or most absorbent colours. 

 The materials from which the best effects have been produced 

 are cottou-wool, worsted, fibrous materials generally, cork, 

 sponge, platinum and other metals in a spongy condition, and 

 lamp-black. 



The loud sounds produced from such substances may perhaps 

 be explained in the following manner: -Let us consider, for 



