NA JURE 



[July 5, 1894 



s supplemented with fuller details by a series of extensive notes 

 on the use of the " Frena," occupying nearly eight times as 

 many pages as the "outlines" above mentioned. These notes 

 contain some sound advice, of which the novice could not do 

 better than take advantage, and they are written in a clear 

 style. The illustrations and figures are exceedingly neat 

 and clear, and the whole get-up of the book is all that can be 

 desired. 



SoM E new facts concerning the natureof the molecule of calomel 

 are contributed to the current issue of the Berichtt by Prof. 

 Victor Meyer and Mr. Harris. The detenniaations of the vapour 

 density of mercurous chloride made by .Miischerlich, Deville 

 and Troost, and Rieth, in each case afforded numbers in close 

 agreement with those demanded by the simple formula HgCI. 

 Odling, however, disputed the possibility of the existence of 

 molecules containing only one atom of each element, involving 

 the assumption of univalency for mercury, and showed that when 

 gold-leaf is immersed in the vapour it becomes amalgamated, 

 indicating the presence of free mercury vapour. Erienmeyer 

 su'raequently showed that this experiment was open to the 

 objection that the amalgamation might be due to a chemical 

 reaction between gold and calomel vapour, and pointed out 

 that the presence of free mercury may be more conclusively 

 shown by immersing a glass tube, cooled by containing a 

 column of quicksilver, in the vapourised calomel, when an abun- 

 dant condensation of mercury globules is observed. Debray 

 afterwards immersed in the vapour of calomel a bent tube of 

 silver, gilded outside and kept cool by the passage of a current 

 of cold water, and found that both mercury and corrosive sub- 

 limate were condensed upon it, but that the greater portion of 

 the sublimate consisted of unchanged calomel. Debray l here- 

 fore concluded that dissociation into mercury and corrosive 

 sublimate only occurred to an insignificant extent. Prof. Meyer 

 and Mr. Harris now show that if a piece of gold-leaf is im- 

 mersed for an instant only in the vapour of calomel it is 

 invariably amalgamated, but if it is allowed to remain in the 

 vapour for a few minutes it becomes pure gold again, the 

 mercury being volatilised. They have further carried out a 

 series of vapour density determinations by Prof. Meyer's well- 

 known method, at the temperature of the vapours of boiling 

 s:ilphur (448°) and phosphorus penlasulphide (518°). The 

 numbers obtained are all in close proximity to that calculated 

 for the molecular condition HgCI, agreeing in this respect 

 with the older determinations above referred to, in which other 

 methods were employed. The calomel was introduced into the 

 apparatus in the form of a compressed pastille, thus obviating 

 the necessity for a containing bulb or tube, and enabling almost 

 instantaneous volatilisation to be achieved. A second series of 

 experiments were then made with a mixture in the proper pro- 

 portions of free mercury and corrosive sublimate, and the results 

 were almost identical with those obtained from calomel. Of 

 course this does not afibul any conclusive evidence, but experi- 

 ments are next described in which .in attempt at identification of 

 the substance or substances present in the vapour was made. 

 It was shown that when the cylindrical bulb of the density 

 apparatus was instructed of porous earthenware, a very large 

 amount of mercury vapour diffused through it, and could be 

 condensed upon an outer envel9ping glass cylinder. Further, 

 that when calomel is vapourised in a retort connected with a 

 Sprengel pump, and in which the pressure has been reduced by 

 the latter to alx>ut 30 mm., the upper portion of the apparatus 

 becomes covered with a layer of mercury globules, and a pro- 

 portionate quantity of mercuric chloride is formed. Chemical 

 evidence it also adduced to prove the |)rescnce of mercuric 

 chloride vapour in the gaseous product of heated calomel, for it 

 ii shown that pieces of caustic potash previously heated to the 

 NO. I 2S8, VOL. 50] 



same temperature become instantly covered with orange-coloured 

 mercuric oxide, just as when plunged into vapour of corrosive 

 sublimate, proving the absence of any large quantities of mer- 

 curous chloride, which would have afforded a black deposit of 

 mercurous oxide. Prof Meyer and Mr. Harris therefore con- 

 clude that when calomel is vapourised it dissociates into 

 mercury and corrosive sublimate, Hg2Cl5=Hg-^ HgCU. and 

 the necessity for the assumption of monadic valency for mercury 

 is thus avoided. 



The additions to the Zoological Society's Gardens during the 

 past week include a Rhesus Monkey (Macacus rhesus, i ) from 

 India, presented by Mrs. McHugh ; three Barbary Turtle Doves 

 (Tur/iir risori»s) (lom North Africa, presented by the Misses 

 E. and P. Mackenzie ; a Common Cuckoo {Ciicu/iis caiiorus), 

 British, presented by Mr. W. Keen ; two Horned Lizards 

 (PJirj'iiosoma coriiiilum) from Texas, presented by Miss Mait- 

 land, an Anomalous Snake [Co>\mella anomala) from South 

 Africa, deposited; an Ostrich {Strul/iio cameliis, 9). from 

 Africa, two Red headed Merlins (Hypotriorchis chiequera) from 

 India, purchased ; an .Ethiopian Wart Hog {Pheuochimi' 

 athicpicus, 9 ), from South-East Africa, received in exchange ; 

 a Tnar (Capra jemlaka, (5 ). a Burrhel Wild Sheep (Ovis 

 biirrhel), a Great Kangaroo (Macropiis giganleus, 9 ), born in 

 the Gardens. 



Prof. W. R. Kisher requests us to make the following cor- 

 rection in his contribution to our last number : — On p. 193, 

 line 8 from top, for "I "025" read "l'02s"." 



OUR ASTRO.XOMJCAL COLUMN. 



The First Oiiservation of Sun-spots. — A contribution 

 to the history of the rival claitns of the various alleged dis- 

 coverers of sun-spots appears in the R^ndiconti d-.i I.iucei, from 

 the pen of ProfJ E. Millesovich. It is a criticism of Dr. 

 Berthold's pamphlet on "Master Joann 1-abricius and the 

 Sun-spots," setting forth the claims of the sou of the Irisian 

 astrologer David Fabricius to the name of the true discoverer 

 of the solar phenomenon in question. The other claimants 

 are, of course, Galileo and the Jesuit Scheiner, known under 

 the name of Apclles. The claims of Fabricius are based upon 

 his book De Maculis in Soltobservnlis, tiarralio, &c., publislied 

 at Wittenberg in 161 1. He had lieeii studying at l.eyden 

 University, whence he brought home l.ippershey's newly-in- 

 vented telescope to his father at Ostccl. The latter was already 

 well known among .islronomers as the discoverer of the 

 variability of Mira Cell. The method of projecting the solar 

 image on a screen is set forth in detail in the work referred to, 

 as well as the correct conclusion that the sun rotates about an 

 axis. Prof. Millesovich grams that the name of Fabricius 

 was probably known to the Jesuits and suppressed as that of a 

 heretic, but he comes to the conclusion that Cialileo was 

 actually llis first ili^coverer, having observed the spots as c.irly 

 as the summer of 1610, whereas Faliriclus saw them indepen- 

 dently on .March 9, 1611, and Scheiner about the same time, 

 without, however, payim; much attention to them before the 

 publication of Fabricius's A'u; /<»//<'. He then observed them 

 assiduously, and collected a large number of valuable records. 



The Procress of Astro.vo.mical Photograi iiv. — Under 

 this title, Mr. H. C. Russell, C.M.G., F.K.S., the tioveri.mcnt 

 Astronomer at Sydney, delivered an address, as President of 

 Section A (Astronomy, .Mathematics, and Physics), at the last 

 meeting of the Austral.' nn Aisociallon for ihe Advanccm;nl 

 of .Science. The addres has now lieen issued, and it is the 

 most complete sialeinenl iLil we have seen ol the advance of 

 astronomical photography from the lime when Prof. J. W. 

 Draper look daguerreotypes ol the uioon, in 1840, to June 1893. 

 The references (lisiiiliuied through ihe address aild to its use- • 

 fulness. Reference is made to ei,;lity-one sources of infonna- M* 

 lion in all, and of these, Natlke claims the large proportion 1' 

 of thirlytwo. Like many other enthusiastic workeis in the 

 realm of celestial photography, Mr. Russell believes that 

 astronomical obseivations will eventually be automatically 

 made by means of the sensitive plate of the photographer. 



