Nov. 7, 1889] 



NATURE 



19 



The Colonies and India states that a discovery has recently 

 been made on a Fiji plantation, which will probably prove 

 extremely valuable in all tropical countries where the cultivation 

 of bananas is regarded as a settled industry. The banana disease 

 had for some time been causing much havoc on a plantation on 

 Vanua Levu, and it appears that the discovery of an antidote 

 was due to an accidental occurrence. On a flat near the sea- 

 shore there was a patch of bananas much diseased, and some 

 time ago the sea swept into it and remained on it for about an 

 hour. All the plants were killed as far as the standing stems 

 were concerned, but vigorous young shoots came up freely from 

 the roots, and were not only quite free from disease, but soon 

 began to bear much larger bunches of fruit than the parent 

 plants ever did. Upon noting this effect the planters deter- 

 mined to try the experiment upon a number of badly diseased 

 plants which the sea had not reached. They cut down the 

 diseased plants, and, having stirred the ground about them, 

 poured from one to four buckets of seawater over each. The 

 result was that, while the parent stems withered, vigorous young 

 shoots came freely away, without a sign of disease. 



A SERIES of successful experiments upon the simultaneous 

 production of pure crystals of sodium carbonate and chlorine gas 

 from common salt are described by Dr. Hempel in the current 

 number of the Berichte. The experiments simply consisted in 

 passing a current of carbon dioxide gas through a solution of 

 salt contained in a special form of electrolytic cell, through 

 which an electric current from a few Bunsen's cells or a small 

 dynamo was circulated. The kathode found mist convenient 

 consisted of a plate of iron or carbon perforated with numerous 

 holes about 4 millimetres in diam2ter, bored obliquely, so that 

 bubbles of gas couM readily escape upwards. For anode a 

 similar plate of thin perforated carbon was employed. Both elec- 

 trodes were circular in shape, and between them was placed a 

 diaphragm of thick asbestos paper, which was directly squeezed 

 between the two plates. This arrangement was found to possess 

 the double advantage of bringing the two electrodes within 

 I millimetre of each other, and so greatly diminishing the 

 internal resistance, and of affording such excellent support to 

 the asbestos diaphragm that any rupture of the latter was 

 entirely prevented. The electrodes and their enclosed dia- 

 phragm were supported in a circular glass cell in such a manner 

 that they divided the cell into two distinct chambers. To the 

 glass wall of the cell on the positive or anode side was fitted a 

 wide side tube, through which the salt was supplied as often as 

 necessary in solid pieces, a little water being also from time to 

 time added to replace that taken up in the crystallization of the 

 sodium carbonate. A delivery tube was also attached to the 

 upper portion of the anode chamber in order to conduct away 

 the liberated chlorine gas. The negative or kathode chamber 

 was supplied at its upper end with an opening serving on the 

 one hand to introduce the carbon dioxide delivery tube, and on 

 the other to extract the crystals of sodium carbonate. The 

 apparatus was thus found to work continuously for weeks to- 

 gether, the asbestos diaphragm withstanding the pressure very 

 satisfactorily. The separation of the soda crystals is readily 

 explained by the well-known fact of the difficult solubility of 

 sodium carbonate in solutions of sodium chloride ; as fast as the 

 electric current decomposes the sodium chloride into chlorine 

 and sodium, the carbon dioxide converts the sodium hydrate 

 formed by the reaction of the sodium upon water into the normal 

 carbonate, which, in presence of the constantly replenished com- 

 mon salt, at once separates in the usual monoclinic form of 

 NaoCOg . loH.^O. The total resistance of the cell is only about 

 five and a half volts, which may be still further reduced by 

 constructing both electrodes of carbon. Using a small dynamo- 

 electric machine, 64'S grams of chlorine and 259 '8 grams of 

 NaaCO^. 10H2O per horse-power of 680 volt-amperes were pro- 



duced per hour, so that the experiments, in addition to their 

 interest from a purely chemical point of view, may turn out to 

 bear fruit technically. The soda produced is stated to be 

 chemically pure, and the chlorine to contain but a verj- small 

 admixture with other gases. 



The additions to the Zoological Scciety's Gardens during the 

 past week include a Patas Monkey {Ccrcopithecus fatas i > 

 from West Africa, presented by the Rev. James Vernall ; a 

 Cheetah {Cymslunts jubatiis i) from South Africa, presented 

 by Captain M. P. Webster, s.s. Koslin Castle ; a Ring-tailed' 

 Coati {Nasua rufa 9 ) from South America, presented by Mr. 

 J. A. Martin ; two Short-toed Larks {Calandrella brachydactyla) 

 from Devonshire, presented by Commander W. N. Latham, 

 R.N., F.Z.S. ; a Sharp-nosed Crocodile [Crocodihis acitlus) from 

 Jamaica, presented by the Jamaica Institute ; two Tuatera 

 Lizards {Sphenodon ftmctatus) from New Zealand, presented by 

 Rear- Admiral Henry Fairfax, R.N., C.B., F.Z.S. ; a Smooth- 

 headed Capuchin (Cf^i^i- vionachtis (J ) from Brazil, deposited ; 

 a Collared Peccary {Dicotyles tajacu ? ), four Rosy-billed Ducks^ 

 {Metoplana peposaca <? d ? 9 ) from South America ; two Grey 



Squirrels {Scitirus cinereus) from North America ; four 



Finches ( Munia nana) from Madagascar, purchased. 



OUR ASTRONOMICAL COLUMN. 



Stellar Parallax by Means of Photography.— Prof. 

 Pritchard has sent us his eminently successful " Researches m 

 Stellar Parallax " by the aid of photography, from observations 

 made at the Oxford University Observatory. The advantage in 

 point of convenience and rapidity in the multiplication ol 

 oVjservations which this method possesses over all others is in- 

 calculable, and it is interesting to note that in the case of 61, 

 Cygni the parallax obtained was o"'4294 ± o"-oi62, and that 

 Bessel's probable error is practically identical with this here 

 stated. Hence, as far as the present results are concerned,, 

 photographic and heliometric measures of parallax may be 

 regarded as possessing an equality of accuracy. 



The following list contains the stars whose parallax has beer> 

 determined by this novel method, and some of the results- 

 obtained : — 



6I1 Cygni . 

 61., ,, 



yct Cassiopeire 



Polaris 



a Cassiopeias 



y " . 

 a Cephci 



-f o'429 ± o 016 



-f 0*432 ± 0019 



+ 0021 db 0*023 



-t- 0"052 ± O'OII 



-f o 035 ± o 024 



-f o"i57 ± 0-036 



- 0*032 ± 0"026 



+ 0*073 ± 0031 



The almost identical parallax of the two components of 6r 

 Cygni is worthy of note. The average of eight determinations 

 gives a value o"*437, which is a close approximation to Dr. 

 Belopolsky's value of 0*50 as the absolute parallax of 6i Cygni. 



Bessel determined a small negative parallax for \x Cassiopeia?, 

 but Dr. Struve ^assigned it a value -t- o"*342. The very small 

 positive parallax given by Prof. Pritchard may be explanatory of 

 Bessel's negative determination. 



The small negative parallax found for 7 Cassiopeia: would 

 indicate that it and the comparison stars are in the same gronp» 

 although its bright line spectrum points to a constitution different 

 from that of other stars in this constellation. 



Even a cursory examination of the summary of results renders 

 it evident that no relation exists between the lustre and parallax 

 of stars, and indeed, since we probably view bodies which are 

 still in various stages of condensation, we should hardly expect 

 to find any such relation. 



Measurements of Double ^iKY.?,.—AstrofiomischeNach- 

 richten, Nos. 2929-30, contain a series of double star observa- 

 tions made with the 36-inch refractor of the Lick Observatory 

 by Mr. S. W. Burnham. The discovery is claimed of two very 

 faint stars in the trapezium of Orion, an<l an excessively faint 

 double has also been detected by Mr. E. E. Barnard just outside 

 and preceding the trapezium. The observers believe that, in: 

 spite of the numerous alleged discoveries of faint stars in this- 



