54^ 



NATURE 



{Oct. 7, 1880 



The Variable R HydR/E. — Dr. Gould, at Cordoba, has 

 given much attention to the changes in this variable star, respect- 

 ing which Argelander remarked that so long as observations were 

 confined to European latitudes little would probably be under- 

 stood, and he has deduced a formula closely representing the 

 observations, excepting one by Maraldi, about \\ hich there appears 

 to be a large error. The earliest recorded observations of this 

 celebrated variable Dr. Gould remarks were those of Hevelius in 

 April, 1662, published in the scarce volume of the " Machina 

 Ccelestis" in 1679. Montanari of Bologna comparing Bayer's 

 Uranometry with the sky on April 15, 1670, remarked it as a star 

 of the fourth magnitude, not entered upon the map, and notified 

 it as a new object. Its variability was recognised by Maraldi at 

 Paris in 1704, who watched it at intervals till 1712. There then 

 appears to be a gap in the observations until we come to those 

 of Pigott in 17S4 and 1785. Argelander collected and discussed 

 all the observations to the beginning of 1S63, and deduced a 

 fonnula which fairly represented the data since 1784. The length 

 of the period is decreasing rapidly, amounting, as Dr. Gould 

 says, to more than nine hours at each successive recurrence — a 

 circumstance which impeded the determination of the number of 

 periods elapsed between Montanari's observation in 1670 and the 

 first maximum noted by Pigott. Twelve periods having elapsed 

 since the latest maximum included in Argelander's investigation, 

 present data allow of clearing up several doubtful points. 



Dr. Gould finds that the number of periods between the 

 maxima of 1670 and 1784 must have been eighty instead of 

 eighty-four, as assumed by Argelander, and the number between 

 the maxima of 1670 and 1704 must have been twenty-three 

 instead of twenty-five. Assuming that Maraldi's second maxi- 

 mum is erroneously dated in 1708, instead of 1707, he finds that 

 all existing observations except Maraldi's first, may be repre- 

 sented within quite tolerable limits, " by supposing a uniform 

 diminution in the period, upon which are superposed variable 

 terms, according to which a symmetric perturbation completes its 

 •cycle in seventy-two years," and the following formula is finally 

 inferred. The days are counted from the beginning of the year 

 1875 :— 



T = 35 "ed. -f 434-445d. K-0'37974d. n^^T,ix>&.im(^ n -f lo°) 

 -f 2-6d. sin(io''« + 324°) -f 6'8d. sin(l5°?; -t- 205°) 



It will be found that the formula fixes the next maximum to 

 January 18, 1881 ; Schmidt alone has observed the minima, 

 which occur on the average at about 9-i6ths of the interval 

 between the maxima. 



A New Comet. — On the evening of September 29 Dr. Ernst 

 Hartwig of the Imperial Observatory, Strassburg, discovered a 

 bright comet about 10° north of Arcturus, and having obtained 

 •observations on three consecutive nights, has calculated the 

 following elements : — 



Perihelion passage, September 6-9528 M.T. at Berlin. 



Longitude of perihelion 80 0'6 



,, ascending node 43 32'3 



IncUnation of orbit 38 4S'3 



Logarithm of perihelion distance 9 '5645° 



Motion — retrograde. 

 Hence he finds, for Berlin midnight : — 



R-A. Decl. Log. distance from 



n. m. s. , , Earth. Sun. 



Oct. 6 ... 16 7 40 ... -4-24 35-5 ... 9-8147 ... 9-9231 



S ... 16 29 22 ... 22 46-2 ... 9-8488 ... 9-9432 



10 ... 16 47 18 ... 21 35 ... 9-8827 ... 9-9623 



12 ... 17 2 15 ... 19 29-6 ... 9-9158 ... 9-9805 



14 ... 17 14 51 .. -H8 5-0 ... 99476 ... 9-9978 



The intensity of light is rapidly diminishing, being on October 14 



only one-sixth of that at the time of discovery. 



The above orbit places the comet at 6 a.m. G.M.T. on 

 September 12 near to Regulus, so that it is distinct from the 

 object notified by Mr. Lewis Swift of Rochester, N.Y. 



The comet was seen for a few seconds between clouds at the 

 Royal Observatory, Greenwich, and at Mr. Barclay's observa- 

 tory, Leyton, on the 5th, and is described by Mr. Talmage as 

 " very bright," with a long tail." 



CHEMICAL NOTES 

 In connection with the subject of water of hydration the 

 results of Van Bemmelen, described in the Berliner Berichtc, 

 are of interest. He has determined the quantities of water 



parted with, and also taken up by various hydrated oxides under 

 different conditions of temperature and humidity of .surrounding 

 atmosphere. The results afford another instance of the graduation 

 of chemical into physical actions. The amount ol water taken 

 up varies but little, but the strength of the combination varies 

 much. The formation of hydrates appears to be a function of 

 molecular weight of the oxide and of the temperature. 



Two papers of great importance by Thomsen have just 

 appeared in the Berliner Berichle. Thomsen attempts to 

 base a general theory of the structure of carbon compounds 

 on thermal determinations. He does this by measuring (in- 

 directly, of course) the heat of dissociation of the carbon mole- 

 cule, and from this and other data, finding a thermal value for 

 the combination of two carbon atoms, to form a gaseous com- 

 pound, by four, three, two, or one " link." Hence he deduces a 

 thermal value for each "link." General equations are given for 

 calculating the heats of formation of various isomers, assuming 

 a certain "linking" of the atoms for each. In cases where 

 various "linkings" maybe assumed, a determination of the heat 

 of formation may determine which "linking," and therefore 

 which structural formula, is the more probable. 



In a paper read before the Onens College Chemical Society 

 Messrs. Bevan and Cross detail experiments on jute fibre, which 

 lead them to regard the intercellular portion of this fibre as 

 probably consisting of an aromatic compound of the quinone 

 class, together with a substance allied to the carbohydrates, and 

 somewhat of the nature of cellulose. The presence of this inter- 

 cellular substance confers on jute the power of retaining various 

 dye-stuffs. The authors also describe a method of separating 

 cellulose from jute fibre, based on the action of chlorine or bro- 

 mine, subsequent boiling with dilute caustic lye, and washing in 

 acid. Jute fibre which has been acted on by chlorine is coloured 

 deep magenta by immersion in a solution of sodium sulphite, 

 nie work of Messrs Bevan and Cross promises results of con- 

 siderable importance. 



Mr. O. Hehner publishes in the Analyst the results of his 

 determinations of phosphoric acid in potable waters. He con- 

 cludes that the presence of more than 0-5 parts per million of 

 P0O5 should be regarded with suspicion ; also that absence of 

 phosphates affords no positive proof of freedom from pollution. 



It is stated in the Chemiker Zeitung that if a solution of two 

 parts of citric and one of molybdic acids be evaporated to dryness, 

 heated to incipient fusion, and dissolved in 30 to 40 parts of 

 water, a solution is obtained which imparts a blue colour to 

 paper immersed in it, and dried at 100". This paper is bleached 

 by water, and may be used as a test for the presence of water in 

 alcohol, ether, &c. 



M. de Schulter states in Complcs rend, that he has succeeded 

 in preparing pellucid crystals of analcite by heating a solution of 

 sodium silicate or caustic soda along with aluminous glass in 

 sealed tubes to about 190°. 



From analyses and determinations of specific heat of cerium 

 tungstate, Cossa and Zecchini {Gazelta chiin. Ilaliaim for July) 

 think that the atomic weight of cerium is better represented by 

 92, the number formerly adopted, than by 1 38, which — or more 

 probably 141 — is generally regarded as correct. The data of the 

 ItaUan observers are as follows : — Ce._,(\V04)3 (Ce= 141) = 1026, 

 X 0-0821 (sp. heat found) = 84-2, atomic heat of W — 6-4, of 

 = 4; hence molecular he.at of ( WO^jj = 67-2, but 84-2 - 67-2 

 = 17, which -^ 2 gives 8-5 as the atomic heat of cerium. 

 CeWOj(Ce = 92) = 340, X 0-0821 = 27-9; but 27-9 - 22-4 

 (that is, molecular heat of WO4) gives 5-5 as the atomic heat of 

 cerium. The careful determinations of the specific heat of 

 metallic cerium made by Hillebrand, and the general analogies 

 of the cerium salts, must however be regarded as of more value 

 in determining the atomic weight of this metal than a series of 

 estimations of the specific heat of a compound containing oxygen, 

 concerning the influence of which element on the specific heat of 

 compounds thereof we have so little exact knowledge. 



There has of late been a considerable amount of discussion 

 as to the existence of pentathionic acid, HjSjOo. In a recent 

 paper in the Journal of the Chemical Society, Messrs. Taka- 

 matsu and Smith bring forward evidence which appears con- 

 clusively to prove that this acid does exist. 



Hell has studied the action of bromine on acids of the 

 acetic series, and in a paper in the Berichle he shows that the 

 substitution of bromine for hydrogen proceeds slowly, until from 



