Oct. 5, 1876] 



NA TURE 



507 



1. A little common salt was placed in a crucible, inclosed in 

 a jackef, and exposed to the Bunsen flame. The fringe of flame 

 appearing above the crucible was of course coloured most in- 

 tensely yellow. 



2. A similar arrangement was made, only that the crucible 

 contained a mixture of common salt and powdered charcoal. 

 Although the crucible was heated to a redness, the flame had lost 

 most notably its intense yellow colour and occasionally a slight 

 blue tinge appeared around the edge. This last I do not lay 

 much stress on, as it might be merely due to the Bunsen flame ; 

 but the diminution of the sodium colour could not be overlooked. 



3. The crucible was now filled with a mixture of salt and 

 powdered charcoal, together with a very little of sulphide of iron 

 (in fact, the substance used for the preparation of sulphuretted 

 hydrogen), and exposed over the Bunsen burner as before. In 

 this case the sodium coloration almost completely disappeared, 

 while the blue flame became very distinct indeed. 



No difference could be observed, whether the air was turned 

 on or off the burner, in these experiments. 



When the above mixtures were exposed on platinum wire in 

 the naked flame, they only gave the sodium colour. This is 

 doubtless to be ascribed to the stronger heat volatilising some of 

 the sodium salt before it had time to enter into the necessary 

 changes. This is the more likely, because mixtures made with 

 just the slightest trace of salt gave the yellow colour in the 

 naked flame, while the mixtures used in the crucible as de- 

 scribed, and which gave the blue colour, contained [fully"5o per 

 cent, of salt. 



Dr. Schuster, in the note already mentioned, refers to a paper 

 by Dr. Gladstone {Phil. Mag., 1862, vol. xxiv., p. 417), on the 

 similar behaviour of certain metallic chlorides in imparting a 

 blue or violet colour to flames of various kinds. I find that in 

 this paper the violet colour given by the chlorides of potassium, 

 sodium, and barium, in the flame of red-hot coals is noticed. 

 Dr. Gladstone remarks, however, that " a doubt must rest on 

 such observations made with a common coal fire, as it is quite 

 conceivable that these chlorides may give up, their chlorine to 

 the alkalies or earths of the ash. 



It struck me that it would have some bearing on the matter, 

 to ascertain if other salts of sodium exhibit the same phenome- 

 non. On trial I find that there is no difference. 



A little pure sulphate or carbonate of sodium thrown on a 

 coal fire produces exactly the same blue flame as common salt, 

 both with ordinary coal and with anthracite. These salts, in 

 the flame of the Bunsen or the spirit-lamp, give the strong 

 yellow flame of sodium at once. It is clear that their behaviour 

 on hot coals is explainable in exactly the same way as that of 

 common salt, viz., by the production of carbonic oxide. It is 

 inferable, therefore, that the blue flame of common salt is not 

 to be ascribed solely to some property inherent in chlorides alone ; 

 and the solution I have proposed seems the more plausible, 



A correspondent in Nature suggested the probable formation 

 by a reaction between common salt and copper pyrites in the coal, 

 of chloride of copper, and that the last would give the blue 

 flame. However, it is iron pyrites, and not copper pyrites, that 

 occurs in coal ; and, moreover, the flame of copper chloride is 

 bluish green, and not blue. Edv/ard T. Hardman, 



Kilkenny Her Majesty's Geological Survey 



OUR ASTRONOMICAL COLUMN 



The Intra- Mercurial Planet Question.— Not- 

 withstanding the suspicious aspect of the spot remarked 

 upon the sun's disk by Weber at Peckeloh, on the after- 

 noon of April 4, 1876, as it is described by him in his 

 letters to Profs. Heis and "Wolf, it would appear that it 

 must be relegated to that class of ordinary solar spots 

 which are better defined than in the majority of cases, 

 and continue visible but a short time. A letter has been 

 addressed to the Abbd Moigno by Senor Ventosa, of the 

 Observatory at Madrid, containing a very definite obser- 

 vation of a spot on that day which was evidently the one 

 noticed at Peckeloh. A similar letter to Prof. Peters is 

 published in Ast. Nach., No. 2106. 



It is not, perhaps, generally known in the astronomical 

 world that the systematic observation of the sun's disk 

 forms one of the routine subjects to which attention is 

 directed at the Madrid Observatory. The observations 

 are made daily with the large Merz-Equatoreal, projecting 



the image of the sun upon a screen so as to present one 

 of considerable diameter. The heliographic positions of 

 the spots arc determined on the method adopted by the 

 late Mr. Carrington on the image projected by the finder, 

 which is provided with a suitable reticule, and, whenever 

 possible, their distances from the limb are measured 

 directly with the large telescope. The drawings are 

 made by hand. 



After noon on April 3 the sun was without spot, a group 

 oifacula only being visible very near the S.W. limb. But on 

 the morning of April 4 there was a small spot, a simple 

 nucleus without penumbra, of an apparently elliptical 

 figure, with a ^m.?CAfacula on the N.W. side (puro nucleo 

 sin penumbra, de figura eliptica aparentemente, y con une 

 facula pequena por el lado N.O.) ; this was very well ob- 

 served. Cirrus was scattered over parts of the sky, but 

 the images were well defined. The observations gave the 

 following results : — 



April 3 at 22h. 9m. 54s. M.T.,at Madrid, angle of posi- 

 tion of the spot, 76° 43', distance from the centre of the 

 disc 8i8"'9, the sun's semi-diameter being taken at 960' 9. 

 At 22h. 24m. direct measure of the distance of the spot 

 from the sun's limb gave 147", consequently 814" for the 

 distance from the centre. The dimensions of the spot 

 were 4" X 2". 



April 5, after noon, the sun was again without spot ; the 

 most remarkable object was a \)x\<^\. facula very near the 

 N.E. limb. It will be seen that the first Madrid observa- 

 tion was made 5h. 7m. previous to that at Peckeloh. 



The opinion expressed by M. Leverrier before receiving 

 the Madrid observation, that certain problematical solar- 

 spot observations upon record might accord with a revo- 

 lution of an intra-mercurial planet in about twenty-eight 

 days, in which case an inferior conjunction might fall on 

 the 2nd or 3rd of the present month, has been construed 

 into a definite prediction of a transit of the so-called 

 Vulcan, on one of those days, a prediction which M. 

 Leverrier distinctly repudiates, though it has been widely 

 circulated by the daily press in and out of France. The 

 rejection of the observation of April 4 in the present year 

 leaves us in doubt again as to what period will correspond 

 to the most reliable data, assuming the existence of an 

 inter-mercurial planet. 



Mr. Wray's observations about midsummer, 1847, and 

 others of hardly less authority, require explanation. It 

 is impossible to repudiate them, but whether referable to 

 the passage of planetary or cometary bodies, must remain 

 for future decision. 



The Variable Star, Algol. — The following are 

 Greenwich times of visible geocentric minima of Algol 

 to the end of the year, calculated from the elements in 

 Prof. Schonfeld's latest catalogue of variable stars : — 



h. m. h. m. 



Oct.Jao ... 1642 Dec. 2 ... 1655 



23 ... 13 21 5 ... 13 44 



26 ... 10 20 8 ... ID 33 



29 ... 78 II ... 7 22 



Nov. 12 ... 15 13 22 ... 18 38 



15 ... 12 2 25 ... 15 26 



18 ... 8 51 28 ... 12 IS 



21 ... S 40 

 The Minor Planets. — It appears by a telegram from 

 Vienna in the Paris Bulletin International, of September 

 23, that Herr Palisa, of the Observatory at Pola, has re- 

 covered No. 66 of the group of small planets — Maia — 

 detected by Mr. Tutde, at Cambridge, U.S., though at 

 some distance from the position given in the Berliner 

 Jahrbuch for 1878. 



The following names are proposed for recent dis- 

 coveries : — No. 165, discovered August 9, 1876, Loreley j 

 No. 166, August 15, Rhodope ; No. 167, August 28, 

 Urda. Nos. 168 and 169 are announced j^the former was 

 detected by Prof. Watson on September 27, and the latter 

 by M. Prosper Henry on the following night neai' the 

 same position. Both are eleventh magnitudes. 



