September 16, 1922] 



NA TURE 



179 



in the average rate of loss of heat by convection, and 

 consequently there is a fall in the temperature, and 

 hence in the resistance, of the grid. The fall in 

 resistance can be measured by a Wheatstone bridge 

 method. The way in which it is suggested that this 

 process may be utilised in the construction of a 

 standard source of sound is as follows. The source 

 is made in the form of a cylindrical Helmholtz reson- 

 ator — say from brass tubing about 2 in. diameter. 

 At one end is fitted a telephone in such a way that 

 the diaphragm forms part of the inner wall of the 

 resonator, while at the other end is the orifice carrying 

 the hot-wire grid. If the telephone diaphragm is 

 made to vibrate by current from a thermionic valve 

 oscillator, and the frequency of the current is adjusted 

 until it is equal or nearly equal to that of the resonator, 

 a pure tone of moderate intensity issues from the 

 orifice. At the same time the hot-wire grid suffers 

 a change of resistance which provides a measure of 

 the amplitude of the vibration in the orifice, and 

 hence of the strength of the source. With a standard 

 pattern grid and holder the change in resistance is 

 about 1 2 ohms when a sound of pitch 200 vibrations /sec. 

 is produced, which is loud enough to be just audible 

 at a distance of 10 feet — the source being placed on 

 the ground in the open. The strength of the source 

 can be varied at will by using a variable series re- 

 sistance or a shunt with the telephone. The use of 

 resonance serves to purify the note which comes from 

 the telephone, but it is desirable in addition that the 

 oscillator should be of such a type that the telephone 

 note is already fairly pure. The use of a very impure 

 note may lead to poor results, as the resistance change 

 will then depend onlv partlv on the amplitude of the 

 fundamental. 



It may be noted that a simple method is known of 

 obtaining the relation between the change in resist- 

 ance of a grid and the amplitude and frequency of 

 the vibration producing it — the motion being simple 

 harmonic. Hence, if the frequency of the vibration 

 is known, the strength of the source (defined as the 

 rate at which fluid is introduced or abstracted at the 

 source) can be found in absolute measure. The 

 amplitude of the waves — or, if preferred, the flux of 

 energy — in the surrounding medium can then be 

 calculated in certain cases. A simple case is when 

 the source is close to a rigid plane. 



Any other means of producing a suitable sound can 

 be used in place of the telephone diaphragm provided 

 it is small enough to go inside a resonator. If the 

 damping factor of the resonator has been determined 

 experimentally, the acoustical output of the primary 

 soivrce inside the resonator can be calculated from 

 the indications of the hot-wire grid in the orifice. 

 The output of the internal source includes (1) the 

 radiation of acoustical energy from the orifice, which 

 has been dealt with above, and (2) work done against 

 viscous forces in the orifice. Unless the orifice is 

 large, (2) is far the more important part, and the 

 radiation losses may be negligible by comparison. 



E. T. Paris. 



Signals Experimental Establishment, 

 Woolwich, S.E.18, Sept. 2. 



Occurrence of the Rare Whale, Mesoplodon Layardi, 

 on the Tasmanian Coast. 



Some years ago, on July 30, 1918, my friend 

 Mr. G. H. Smith of Leprena, Southern Tasmania, 

 brought me word that a beaked whale, " without 

 teeth," had been cast up on the beach at Recherche 

 Bay near his property, that he had already removed 

 the blubber, and that the carcase still remained on 



NO. 2759, VOL. I io] 



the shore. Being occupied at the time with university 

 teaching I was unable to visit Recherche Bay till 

 some weeks later. High seas were then running, and 

 the remains had been lifted by these and thrown 

 farther up on the basaltic boulders w'tdch strew the 

 beach at this spot. This resulted in some consider- 

 able damage to the skeleton. Nearly all the ribs 

 were broken, some into three or four pieces, and 

 many of the neural spines had been smashed from the 

 vertebrae. The skull was also damaged, although 

 some of the flesh and integument was still adhering. 



The body was naturally in a somewhat decayed 

 and pulpy condition, but with Mr. Smith's help I 

 was able to salve the remains and so obtain the skele- 

 ton. This is almost complete and is now in my 

 Department. 



My friend was good enough to hand me some 

 measurements and notes which he had made and these 

 I reproduce. The animal " was a female whale. The 

 total length was about 18 ft. ; its jaws were 2 ft. 6 in. 

 long, about 4 in. in diameter at the end, no teeth 

 above the gums. Fins 2 ft. long, 8 in. wide, and 

 tapered, not round like the black whale type. Its 

 flukes were about 4 ft. wide ; it had the appearance 

 of a fast fish as it was rather thin in the body. There 

 was a small fin on its hump, about a foot high, with 

 a decided rake towards the tail. The colour the same 

 as the sperm whale, dark grey and light underneath." 

 Mr. Smith further states that the blubber yielded 

 50 gallons of oil of the finest quality, and that he 

 believes that the animal was driven ashore by 

 " killers," of which there were a number in the bay 

 at the time. There were, however, no marks of 

 injury on the body. 



The matter of recording this specimen seems called 

 for, particularly in view of the description by Mr. 

 E. R. Waite, director of the South Australian Museum 

 (Rec. S. Aus. Mus., vol. ii., No. 2), of the discovery, 

 on the South Australian coast, of an immature male 

 of this species of Mesoplodon. The Tasmanian speci- 

 men was a female and mature, as is witnessed by the 

 condition of the skeleton and by the fact that the 

 pulp cavity of the tooth is entirely closed below. 



The form of the tooth corresponds exactly with 

 that figured by Gray for his Callidon guntheri (Ann. 

 Mag. Nat. Hist., 1871), which, as Flower and Turner 

 suggested, was a female of the present species. It 

 seems now that we must conclude from Waite's 

 description that the mature condition of the tooth in 

 the female represents a stage which is earl}' passed 

 through in the male. 



No pelvic bones were discovered, nor was there any 

 trace of the denticles found in the integument of the 

 jaws of other species. The oil has a density of o-88 

 at i2-5° C. This whale has now been recorded 

 from the coast of every Australian State except 

 Victoria and West Australia. 



T. Thomson Flynn. 



University of Tasmania, Hobart, July 20. 



Atoms and Electrons. 



On the basis of any theory of atomic structure 

 which classifies the elements according to rare gas 

 type, cerium and thorium should be comparable with 

 one another, since the atoms of each are possessed of 

 four electrons more than those of the corresponding 

 inert gases, xenon and niton respectively. There 

 are, however, in the thorium atom, thirty-two more 

 extra-nuclear electrons than in the cerium atom. In 

 spite of this fact, it appears that the distances between 

 atomic centres in crystals of these elements are practically 

 the same (Ce = 3-62A.U. and Th = 3"56 A.U., according 

 to Hull), the distance being, if anything, slightly the 



