August 9, 1894J 



NA TURE 



3^1 



meter needles, the relative position of which could be adjusted, 



anil thus the "pitch" of the resonator altered. The resonator 



liowing the effect of the electric component consisted of a 



if fine silver wire with its axis vertical, the two ends being 



■connected to two cylindrical quadrants. In each case the 



«ires, &c. , were fixed to a light glas> rod, and the whole was 



'suspended by a fine quartz fibre. The author finds that both 



'types of instrument behave in the same manner, and that the 



effect increases as the pitch of the resonator approaches unison 



■iih the vibrator, suddenly changing sign when this point is 



I -ed. Thus, when the resonators were tuned higher than the 



viiirators, they were attracted, while when they were turned 



[.H cr, they were repelled. The effects of slow changes of 



[I .t'.ntial and electrostatic charges produced thereby did not 



aii'^ct the instruments, since the author found that when the 



lis of the induction coil were so far separated that no spark 



1, and therefore no electrical oscillations were set up, 



JiL resonators were unaftected. 



An interesting contribution to the subject of electrical oscil- 



.Tiiuns and electrical resonance is made in a paper by Mr. 



lohn Trowbridge in the current number of the Philosophical 



U I 'iizine. Being desirous of investigating the conditions 



inkr which the formulae given by Kelvin, Stefan, and others 



ir the time of oscillation hold, and considering that method 



lirst employed by Spottiswoode of exciting a Ruhmkorff coil, by 



ITieans of an alternating current dynamo, was a much more 



iinverful method of exciting oscillations than the ordinary 



iicthod of charging Leyden jars by means of an electrical 



n.ichine, or working an induction coil by a primary battery, 



liL- author has designed a form of apparatus in which he employs 



111 alternator capable of giving a current of from 15 to 25 



iiupcres with a potential difference of 120 volts, together with 



I uitable transformer to obtain the necessary difference of 

 I iitial. He, in general, employs one primary circuit between 



entirely separate and disconnected secondary circuits, so 



. , :iL,'(_-d that the images of the sparks in the three spark-gaps, 



ifirr I'. ;li--ction in a rotating mirror, could be formed side by 



' .11 the same photographic plate. The most striking results 



lined by the author are that a unidirectional spark (non- 



-illatory) always excites an oscillatory discharge in a second- 



II y circuit if the self-induction, capacity and resistance of 

 his circuit permit an oscillatory movement. In every case the 

 ir-t effect of the exciting unidirectional primary spark is to 

 make the secondary circuit act as if there were no capacity in 

 IS circuit, a thread-like spark resulting, which is exactly like 

 hat produced when all the capacity in the secondary circuit is 

 •emoved. After a short interval of time the electricity rushes 

 nto the condensers, and begins to oscillate, the strength of the 

 oscillations rising, after one or two vibrations, to a maximum, 

 ind then decreasing : the rate of oscillation finally assuming a 

 teady state, and being expressed by the lormula I — 2 it V i7c. 

 If a unidirectional primary spark excites oscillations in neigh- 

 bouring circuits which are slightly out of tune, the phenomenon 

 )( electrical beats or interferences can be produced in these 

 :ircuits, and is very clearly shown on the photographs of the 



parks. If the primary spark ceases to be unidirectional, and 

 becomes oscillatory, these oscillations will tend to compel those 

 of the secondary to follow them, and if they are not sufficiently 

 powerful to do this they beat with the sec mdary oscillations. 

 When all capacity is removed from the secondary circuits they 

 oscillate in tune with the primary circuit. The author has been 

 led to suspect that there is a change in the period of electrical 

 oscillations when an iron wire is substituted for a copper one 

 jf the same geometrical form, and is at present engaged in 



nvesligating this point. 



NO. 1293, VOL. 50] 



The forty-first report of the Department of Science and Art, 

 and the Directory (revised to June 1S94), have been issued. 



Messrs. Dulau and Co., have issued a catalogue of works 

 they have for sale, on astronomy, terrestrial magnetism, and 

 meteorology. 



We have received from the publishers (Messrs. Bliss, Sands, 

 and Foster) the latest volume of their very pretty series, entitled 

 " The Country Month by Month." Toe number treats of " The 

 Plant-World in August," and "Wild Life" in the pleasant 

 month upon which we have just entered. The series should be 

 a favourite one with lovers of nature, the style of writing in it 

 being bright and chatty, and the general get-up very tasteful. 



A REPORT, just received from Mr. Joseph Baxendell, showing 

 the results of observations made in connection with the meteor- 

 ological department of the Corporation of Southport during 

 1S93, does credit to municipal meteorology. The report includes 

 tables showing the results of routine observations, and also 

 various notes relating to the instruments used and methods 

 employed. 



Mr. J. D. Potter has sent us "Twelve Charts of the 

 Tidal Streams of the North Sea and its Coasts," which he 

 has recently published for Mr. F. Howard Collins. The two 

 thousand arrows which are to be found upon the charts repre- 

 sent the direction of the tidal streams of the North Sea and its 

 surrounding coasts at all hours of the tide upon any day of the 

 year. The time of high water at Dover supplies the key. The 

 charts are reduced from the one published by order of the 

 Lords Commissioners of the Admiralty, and numbered 2339. 



The first number of Contributions from the Zoological 

 Laboratory of the University of Pennsylvania has been 

 received. It contains three articles, as follows, and is illus- 

 trated by four plates : — " The Correlations of the Volumes and 

 Surfaces of Organisms," by Dr. J. A. Ryder ; "The Growth of 

 Etiglcna viridis when constrained principally to two Dimensions 

 of Space," by Dr. J. A. Ryder ; '" Descriptions of three new 

 Polychaeta from the New Jersey Coast," by J. P. Moore. The 

 new serial is issued through the Pennsylvania Press, 

 Philadelphia. 



Yet another magazine professing to be devoted to science has 

 appeared— 77;<iV«a/ Science Revie-M : a Miscellany of Modern 

 Thought and Discovery. The latest arrival, which will be pub- 

 lished quarterly, hailsfromAmerica,but hasanofficein Henrietta 

 Street, Covent Garden. Some of the articles in the first 

 number seem to us scarcely to fall under the head of science, but 

 this lapse into other realms may be due to the fact that the 

 magazine aims at originality. Among the articles somewhat 

 more closely allied to science than those we have hinted at, may 

 be mentioned— "The Mystery of the Ice-age and its Solution," 

 by Major-General Drayson ; " The Problem of the Pole," by 

 C. Morris; and "Nikola Tesla and his Works," by Lieut. F. 

 J. Patten ; while Prof. A. Heilpin contributes " Current 

 Scientific Discussion." 



Both physical and natural science are fairly represented in 

 the current number of Science Progress. Dr. D. H. Scott 

 surveys recent work on the morphology of tissues in the higher 

 plants ; St. George Mivart makes some critical remarks on the 

 theories of epigencsis and evolution ; and Prof. E. Waymouth 

 Reid describes electromotive phenomena in glands. The 

 arrangement of the molecules in a crystal, forms the subject of 

 an interesting article by Mr. H. A. Miers ; and a useful paper 

 on atomic weights is contributed by Mr. Alexander Scott. In 

 the July number of the journal the titles of chemical papers 

 which appeared in May were enumerated. .\ similar list for 

 June is given in the current issue, and an editorial note informs 

 us that the list will be continued in each number. 



