6oo 



NATURE 



[October i6, 1890 



only remedy was to cut down and burn all the trees attacked. 

 Dr. Calves, however, endeavoured at the time to convince the 

 Academy that this was an error, and that the disease proceeded 

 from an hemipterous insect of the genus Coccus, which he clas- 

 sified as Diaspis vandalicus, and afterwards Dr. Valdes Domin- 

 guez, of Baracoa, confirmed this opinion. Finally, at the end 

 of last year, Dr. Carlos de la Torre, a member of the Academy, 

 set all doubt at rest, and proved that the Uredo referred to by 

 the Commission did not even exist in the cocoa-nut trees, and 

 that the small stains which had been mistaken for it were normal 

 to the plant, and existed both in the healthy and attacked trees, 

 and that the real cause was the Diaspis vandalicus of Galves, 

 together with three other species of Coccus. The first symptom 

 of the disease is the appearance on the under side of the leaflets 

 of the fronds, of small white stains, almost imperceptible. These 

 soon attain the size of a pepper-corn, and impart a general 

 white colour to the leaflets, which change, later on, to yellow, 

 and finally dry up. 



The additions to the Zoological Society's Gardens during the 

 past week include two Black-eared Marmosets {Hapale penicil- 

 latd) from South-East Brazil, presented by Captain C. Crawford- 

 Caffier, R.N, ; an African Civet Cat {Viverra civettd), a Two- 

 spotted Paradoxure {Nandinia binotata) from West Africa, 

 presented by Lieut. -Colonel W. Gordon Pachett, W.I.R. ; a 

 Serval {Felis serval) from West Africa, presented by Mr. J. H. 

 Cheetham, F.Z. S. ; two Long- fronted Gerbilles {Gerbillus 

 longifrons <J ? ) from Western Asia, presented by Mrs. F. A. 

 Kitchener ; two Blackcaps (Sylvia atricapilla), a Garden 

 Warbler (Sylvia hortensis), British, presented by Mr. J. 

 Young, F.Z.S. ; three Passerine Parrots (Psittacula passtrina) 

 from Brazil, presented by Mr. Arthur Robottom ; a Bar- 

 nard's Parrakeet {Platycercus barnardi) from Australia, pre- 

 sented by Mrs. E. M. Temple ; a Golden Eagle {Aquila 

 chrysa'dus) from Morocco, presented by Mr. Charles A. Payton ; 

 a Snowy Egret {Ardea candidissima) from America, presented 

 by Mr. H. H. Sharland ; a Herring Gull {Larus argentatus), 

 three Lesser Black-backed Gulls (Larus fuscus), British, pre- 

 sented by the Hon. J. S. Gathorne Hardy, M.P., F.Z.S. ; two 

 Purple Porphyrios (Porphyrio cceruleus) from Sicily, presented 

 by Mr. J. I. S. Whitaker ; a Common Chameleon (Chamceleon 

 vulgaris) from North Africa, presented by Mrs. Wanklyn ; two 

 North African Jackals (Canis anthus) from North Africa, 

 deposited; two Philantomba Antelopes (C^/Zza-^t?^/^?/^ maxwelli 

 6 ? ) from South Africa, three Passerine Parrots (Psittacula 

 passerina) from Brazil, a Lucian's Parrakeet (Palceornis luciania 

 i ) from China, purchased ; six Esquimaux Dogs {Canis 

 familiaris var. 4 (J 2 ? ), born in the Gardens. 



OUR ASTRONOMICAL COLUMN. 

 Objects for the Spectroscope. 

 Sidereal Time at Greenwich at 10 p.m. on October 16 

 23h. 41m. 28s. 



Remarks. 

 (i) The spectrum of this nebula has not yet been recorded. 

 It is described as "considerably bright ; pretty small ; round ; 

 pretty suddenly brighter in the middle." 



NO. 



1094, VOL. 42] 



(2) This remarkable planetary nebula was stated by LasseU 

 to be bi-annular, consisting of a nucleus and two rings, whilst 

 Lord Rosse observed a spiral structure. Herschel described it 

 as "a very remarkable 'planetary nebula; very bright; pretty 

 small ; round ; blue." The spectrum is also a remarkable one, 

 consisting of the three ordinary lines of the nebula?, and, in addi- 

 tion, a line near wave-length 470, which was first seen by Dr. 

 Huggins. This line occurs only in this nebula, with the excep- 

 tion of the Orion nebula, where it has been recorded by Mr. 

 Taylor, and is also feebly impressed in Mr. Lockyer's photo- 

 graph of the spectrum. It is, however, far brighter in the 

 planetary nebula than in the Orion nebula. It has been sug- 

 gested that the line is really the blue band of carbon under such 

 conditions that most of the light is concentrated at about wave- 

 length 470, as is sometimes the case in the laboratory. If this 

 be so, it ought not to be so sharply defined as the other lines, 

 and an observation should be made with reference to this point. 

 Other lines, especially near the carbon flutings in the green, 

 should also be looked for. 



(3) The spectrum of this star, according to the observations of 

 Duner, is undoubtedly a banded one, but whether it is one of 

 Group II. or Group VI. is doubtful. The strongest band is in 

 the red, and this is very little degraded. In the green there is 

 another band, which is wider but not so strong. With less cer- 

 tainty other bands were detected in the red and yellow-green, 

 and another " very vaguely " in the blue. The spectrum is well 

 worth further investigation, as we are likely to learn most 

 by a study of the apparent departures from the regular types. 



(4) A star of the solar type, with fine lines (Konkoly). The 

 spectrum should be further examined as to whether the tempera- 

 ture is increasing (Group III.) or decreasing (Group V.). The 

 fineness of the lines tend to show that it is the latter. 



(5) A star of Group IV. (Konkoly). 



(6) The spectrum of this variable, according to Gore's Cata- 

 logue, has yet to be determined, and the forthcoming maximum 

 of October 19 may therefore be taken advantage of. The period 

 is about 169 days, and the magnitude ranges from 8'3-9"o at 

 maximum to < I2"8 at minimum. 



(7) This variable of Group II. will reach a maximum about 

 October 21. The period is about 326 days, and the variation 

 from 7 -4-9 'Oat maximum to < 13 at minimum. Bright lines 

 and carbon flutings should be looked for. 



(8) This well-known variable of Group II. will reach a maxi- 

 mum about October 24. The range is small (4 -3-4 "6) and the 

 period short (46 days), two conditions which appear to go 

 together, exactly as is demanded by the collision theory of this 

 kind of variability. Further, if that explanation be correct, it 

 is not likely that bright lines will appear at maximum, and this 

 may be made a test observation. A. Fowler. 



Theory of Solar Radiation. —Mr. W. Gofif has written a 

 pamphlet in which he propounds a theory of the sun's radiation 

 of heat. It is well known that geologists and physicists demand 

 a much longer duration of the sun's past activity than the present 

 estimate of the expenditure of heat would allow, supposing that 

 there have been no unknown means of supply. Dr. Croll, in 

 " Stellar Evolution," brings forward evidence in support of the 

 longer periods. To account for the great disparity that exists 

 between the results arrived at from different points of view, he 

 assumed that the primitive nebulous mass possessed a store of 

 energy derived from the impact of two large cold bodies moving 

 with enormous velocities. Mr. Goff also thinks that the grounds 

 upon which geologists and biologists found their conclusions 

 are more certain and trustworthy than those of the physicist. He 

 does not, however, supplement gravitational energy by energy 

 derived from other sources, in order to account for the sun's out- 

 lay, but shows that the methods adopted for arriving at values 

 of the amount are at fault. In his words : — "Radiant energy is a 

 very different thing from absorbed heat, and I have endeavoured to 

 demonstrate that its value must be considerably less. Also I have 

 shown that the current estimates of the sun's annual loss of heat 

 are founded entirely on an absorbed heat basis. They must, 

 consequently, if my arguments are correct, be far in excess of 

 what his expenditure actually is." The distinction between 

 radiant energy and absorbed heat is clearly indicated, and it is 

 evident that, unless the value of each is the same, the present 

 determinations of the sun's emission of heat must be incorrect. 



The Satellites of Saturn. — The micrometer measures of 

 the satellites of Saturn made by Dr. Hermann Struve with the 

 30-inch Pulkova equatorial, has led to some interesting and im- 



