Oci. 25, 1888] 



NATURE 



021 



If I may venture to forecast the manner in which 

 these statements may receive from independent sources 

 that verification which any statement requires before 

 it can be accepted as a correct representation of 

 fact, I should say that as regards § I. no contradiction 

 will arise unless the first case tested should happen 

 to be that of a person with the heart occupying an 

 unusually median position, when the favourable and un- 

 favourable cases, though still distinguishable, may be less 

 so than if the heart occupied its usual oblique position 

 pointing to the left. In any case, however, the variation 

 will be found more marked with a favourable than an un- 

 favourable combination. As regards § II., the statements 



made can be verified as soon as tested upon a recently 

 killed cat or upon a properly educated dog. The veri- 

 fication of § III. only requires that a suitable case 

 should be discovered. As regards the character of the 

 variation, it is probable that its diphasic character may 

 be overlooked at the first glance, but (in a favourable 

 case) this character will soon be apparent. As regards 

 direction, that of the second phase will be determined 

 without much difficulty, but that of the first will be found 

 very difficult to seize. I was not able to make up my 

 mind about it until I had obtained successful photographs 

 of the movements on a quick-travelling sensitive plate. 



Augustus D. Waller. 



THE MAXIMUM OF MIRA CETI. 



I AM anxious to call the attention of observers to the 

 present spectrum of Mira, which arrived at its 

 maximum brilliancy on the 15th inst. I pointed out 

 recently (Nature, May 24, p. 79) that stars of the group 

 to which Mira belongs are sparse meteorite-swarms like 

 comets, and that, when variable, the variability is produced 

 by collisions between two swarms, the centres of which 

 are nearest together (periastron passage) at maximum. 



Broadly speaking, then, we may regard variables of 

 this class as incipient double stars, or condensing 

 swarms with double nuclei, the invisibility of the com- 

 panion being due to its nearness to the primary, or to its 



faintness. It is obvious that variability will occur mostly 

 in the swarms having a mean condensation, for the reason 

 that at first the meteorites are too far apart for many 

 collisions to occur, and that, finally, the outliers of the 

 major swarm are drawn within the orbit of the smaller 

 revolving one, so that it passes clear. 



The present maximum of Mira tests my hypothesis, 

 and its brightness is such that a small telescope and a 

 Maclean's spectroscopic eye-piece are all that are neces- 

 sary to see in how striking a manner the test is borne. 

 The two brightest bands now visible are at X 517 and 

 X 546, precisely where these are seen in the brightest 

 comets. The former is the brightest carbon fluting seen 

 in the spectrum of the Bunsen flame, or spirit-lamp, 



and the other, at 546, is the citron carbon fluting begin- 

 ning at 564, but modified by the masking effects of the 

 manganese absorption fluting at 558, and also that of 

 lead at 546. 



The blackness of the spaces between the bright flutings 

 shows that there can be very little continuous spectrum 

 from the meteorites, and therefore that the absorption is 

 that of the light of the carbon flutings. 



The mean spectrum of Mira is that of a star like 

 j3 Pegasi, which I have shown to consist of bright carbon 

 flutings, and dark flutings of magnesium, manganese, 

 iron, lead, and barium. In 8 Pegasi, as in Mira under 

 mean conditions, the carbon is somewhat faint, but in 

 a Herculis it is very bright. The general effect of the. 

 conditions of maximum of Mira therefore seems to bej 



that of changing its spectrum from one like that of /S 

 Pegasi to one like that of a Herculis. 



I observed that the principal carbon fluting at X 517 

 was somewhat brighter on the 14th than on the 17th inst. 

 In variable stars of this class the proof is now complete 

 that the increase of luminosity is accompanied by 

 cometary conditions, and that it is due to the increased 

 radiation of carbon. 



In the accompanying figure the spectrum of Mira is 

 compared with that of 8 Pegasi and Encke's comet. In 

 some comets the carbon fluting is cut off at 546, exactly 

 as it is in Mira. The observations of Mira were made by 

 myself at Westgate, those of J3 Pegasi by Mr. Fowler at 

 the Astronomical Laboratory at South Kensington. 



J. Norman Lockyer^ 



