March 4, 1880] 



NATURE 



433 



ruary, tSbo. — Rev. W. II. Dallinger, on a series 'of experi- 

 ments made to determine the thermal death-point of known 

 monad germs when the heat is endured in a fluid (PI. I and 2). 

 — Dr. P. M. Duncan, on a part of the life-cycle of Clat/ircystis 

 (Kvitzing). — Prof. E. Abbe, sjme remarks on the 

 apertometer. — A. D. Michael, a further contribution to the 

 knowledge of British 1 (PI. 3 and 4). With 



nee of C. F. George the life histories of fifteen species 

 arc mentioned as traced fir thefir.-t time, the same number are 

 as new to the British fauna, and of these four are new- 

 species, five have been previously found in France, four in 

 Germany, one in both of the c countries, and one in Spits- 

 bergen. Part 2, with two more plates, is promised in the April 

 -1 i. Gulliver, the classificatory significance of raphides 

 ngea. — W. Teasdale, on a simple revolving object- 

 ive record of current researches, bibliography, and 

 .- ciety. 

 Zeitxhrift fur wissenschaftlu Bd. 33. Heft 4. 



23. — Dr. Philipp Stohr, on the history of the de- 

 velopment of the skull in the Urodela, pi. 29, 30. — Karl 

 Richard Krieger, on the minute structure of the central nervous 

 system in the crayfish, pi. 31, 33. — Dr. Julius Krneg, on the 

 fissures of the cortical surface of the cerebral hemispheres of the 

 lonoplacenlal mammals, pi. 34. 3S. — J. Ciamician, on Lafoi'a 

 sp. n., pi. 39, figured on a species of Aglaophenia, 

 rieste. 



Reale htitiito Lombardo di Set .; Rendiconti, vol. 



xiii., fasc. ii. — On the trichamccba irta of De Fromentel and 

 Me. Jobard-Muteavt, by Prof. Maggi. — On the transmission of 

 heat between two fluids in motion separated by a solid wall, by 

 Dr. Gra-si. — On some geometrical and mechanical relations 

 concerning lines of double curvature, by Prof. Baidelli. 



"Journal of the Franklin Institute, January. — Locomotive 

 .-park-arrtstei s, by Mr. J. S. Bell. — Standard sizes in cylindrical 

 fitting, by Mr. Richards. — Saws, by Dr. Grimshaw. — On the 

 method of milk shipment in glass jars, by Dr. Morris. — Velocity 

 of light, by Dr. Chase. 



'iana, fa=e. i. — Cry .-tall ..graphic study of 

 lances of the aromatic series, by Signer La Valle. — 

 Further observations on digallic acid, by S. Schiff. — Contribu- 

 tion to the chemical history of the Stereocaulon Vesuviinum, by 

 S. Coppola. — New method of determining the points of fu-ion 

 of organic substances, by S. Roster. — Researches on podophyllum, 

 I y S. < lUareschi. — Chemical study of the meteorite of Albarello, 

 by S. Mai-.-en. — Chemical researches on the yellow incrustations 

 of the Vesuvian lava of 1631, by S. Scacchi. 



SOCIETIES AND ACADEMIES 

 London 



Royal Society, February 26. — " On some of the Effects 

 produced by an Induction Coil with a De Meritens Magneto- 

 Electric Machine.'' By William Spottiswoode, P.R.S. 



In the Philosophical Magazine for November of last year I 

 pave an account of a mode of exciting an induction coil by the 

 direct application of one of M. de Meritens's alternating machines, 

 without the intervention of a contact-l.reaker or the use of a 

 condenser. The experiments of Prof. Dewar, de-enhed before 

 the Royal Society (see Proceedings, February 13, 1SS0), have led 

 me to think that an account of some of the peculiarities in the 

 induced discharge, might be acceptable to the Society. 



And, first, as regards the secondary discharge in air. It was 

 mentioned in the paper first quoted that the spark produced by 

 this machine presented an unusually thick yellow flame, and that 

 i: was accompanied by a hissing noise different from that com- 

 monly heard w ith a coil excited by a battery. The spark was 

 observed in a revolving mirror, first in a vertical and secondly in 

 .1 il direction. The discharge, although apparently con- 

 tinuous, was immediately seen to be intermittent, with a period 

 in unison with that of the machine. Tongues of flame, leading 

 ".'.ternately from one terminal and from the other, crossed the 

 field of view. The length of spark first used (vertically) was 

 about half an inch. When the length was increased to about 

 two inches flashes] or bands of continuous light were seen to 

 traverse the field of view in diagonals of low slope (i.e., nearly 

 horizontally), showing that there were masses of heated matter 

 passing from time to time at moderate velocity between the 

 terminals. From the known period of the machine and the 



1 by these flashes in their pa-sage 

 from terminal t:> terminal, it was calculated that the time of 

 passage was about "03 of a second. Occasionally there was a 

 still brighter flash or meteor, which similarly traversed the field, 

 but with a velocity apparently of about double that of the 

 others. 



On observing the discharge (vertical) in air attentively, it wa- 



noticed that whenever a true spark passed, its passage was 



marked, as usual, by an irregular bright line when its path was 



outside the aureola or flame, but by a similar dirk line when its 



is within the aureola. 



The spectrum of the secondary spark v. a; then examined with 

 terminals of various metals. 



.- "1 he spectrum showed a faint continuous back- 

 ground with the yellow .-odium lines, and faint oxide of 

 aluminium lines. This was with a spark of half an inch, litit 

 although [he spark was .subsequently lengthened, no difference in 

 the spectrum was perceived excepting that the continuous b tck 

 ground was rendered more bright. 



It would seem that these appearances are due to some such 

 pr ice-s as the following: — The heat due to oxidation, added to 

 that of the discharge, is sufficient to volatilise the oxide of 

 aluminium, but that in its passage across the interval between 

 the terminals, the oxide becomes so cooled that it gives a con- 

 ectrum. When the spark was lengthened, the oxide, 

 although perhaps at first m jre heated than with the shorter spark, 

 had more time to cool. 



ium. — In this, as in the former case, we have a faint 

 continujns spectrum as a background, on which were seen the 

 b group of magnesium lines. One other line in the blue occa- 

 sionally flashed out, but was not permanently present. There 

 was also a faint trace of the oxide spectrum. The contrast 

 between the cases of aluminium and magnesium, in respect oi 

 inence of the oxide, or of the true metallic spectrum, is 

 doubtle-s due to the fact that in the former case the oxide, and 

 in the latter the metal, is the one which is more ea-ily vaporised. 

 On sending a blast of air on the discharge, the blue line always 

 disappeared; the current of air having lowered the temperature 

 so far as to prevent the vaporisation necessary for its production. 



When the spark between magnesium terminals was made to 

 pass through hydrogen, the characteristic Ii es of hydrogen were 

 seen, apparently owing to a rise in temperature. This, us 

 men ioued below, does not occur with carb >n poles. 



m. — With terminals of this metal the spectrum was 

 mainly continuous, with the addition of the ubiquitous yell iw 

 sodium lines. When the spark was short, a few bands were 

 faintly visible, some apparently tho.-e of nitrogen, and other, in 

 the blue and violet belonging to the oxide of platinum. When 

 the spark was lengthened the e bands disappeared, and nothing 

 but the continuous spectrum (with the D Lines) was visible. 



It appears from these experiments that the application of the 

 De Meritens machine to the induction coil furnishes us with the 

 means of isolating certain lines of the metallic spectrum from the 

 rest. It has, in fact, enabled us to reduce at pleasure the spectra 

 of aluminium, of magnesium, and of platinum, to their most per- 

 sistent lines, precisely as had already been noticed as occurring 

 by natural pi •oce.-scs in the cases of sodium and of calcium. As 

 a general rule, when the spark is shortened, the metallic or the 

 oxide lines come out, when it is lengthened they disappear. 



From this we may conclude (1) that the discharge which we 

 have been examining is a real flame with metallic particles pass- 

 ing between the terminals in a solid condition ; and (2) that in 

 general the temperature is comparatively low, i.e., that it is 

 insufficient to cau-e any considerable vapori.-ation. This is 

 notably the case when the arc is long, and when the matter 

 thrown off from the terminals has sufficient time in its passage to 

 cool. 



The spark wa; then tried between carbon terminals in atmo- 

 spheres of hydrogen and of carbonic acid. In none of them did 

 the spectrum show any gas lines, but with hydrogen there were 

 faint traces of the hydrocarbon group in the green. In this 

 respect the spark differs from the discharge direct from the 

 machine, inasmuch as the latter gives some of the hydrogen lines 

 n hydrogen and carbon line- in carbonic acid. 



When magnesium terminals were used in an atmosphere of 

 hydrogen, the yellow sodium lines, the blue and green magnesium 

 1 the red line of hydrogen were visible near the 

 terminals, with a continuous background. When the magnet 

 was excited, the only change observed was that the lines became 

 slightly fainter. 



