464 



NATURE 



\AMgust 19, 1878 



Union Pacific railroads, the Pullman Palace-Car Company, 

 and the American and Union Pacific Express companies 

 made the most liberal arrangements, and Mr. Galbraith, 

 the superintendent of the Repair Works at Rawlins, gave 

 us the free use of his private house and grounds. Of the 

 citizens of Rawlins it is only necessary to say that we 

 never even put the lock on the door of the observatory, 

 and not a thing was disturbed or misplaced during our 

 ten days' residence, though we had many visitors. They 

 sent U5 away with a serenade. Henry Draper 



LETTERS TO THE EDITOR 



■ \The Editor does not hold himself responsible for opinions exp:essed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond -with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communications. 

 \ The Editor urgently requests correspondents to keep their letters as 

 short as possible. The pressure on his space is so great that it 

 is impossible otherwise to ensure the appearance even of com- 

 munications containing interesting and novel facts.l 



Floating of Solid on Molten Metal 



I OBSERVE in Nature (vol. xviii. p. 397) a note of some 

 experiments on this subject. The results of these experiments 

 (unless with lead) are, I think, very similar to some which I 

 have made, and described in your pages (see Nature, vol. xvi. 

 p. 23), viz., that with heavy pieces the metal first sank and then 

 .rose 4o surface ; with light pieces the "skin" formed on the 

 surface of the ladle was sufficient to keep them afloat. From 

 these experiments I drew the conclusion that the cold solid 

 metal was specifically heavier than the molten metal, but after a 

 short immersion, depending on size of pieces, these pieces had 

 expanded by the great heat around them so as to have their bulk 

 increased sufficiently to enable them to float. My experiments 

 with solid pieces of lead showed that they sa7ik and did not come 

 to the surface, and could be felt lying at bottom. Pieces of 

 ^heet lead rolled up floated. 



In some recent experiments which I made, I found that cold 

 pieces pf steel rails placed in a furnace of molten steel sunk at 

 first and floated afterwards, but that hot. pieces floated, and did 

 not sink. W. J. MiLLAR 



,. 100, Wellington Street, Glasgow, August 10 



A Meteorite ? 



This day, at 12. 15 p.m., I was considerably startled by what 

 was to me a remarkable phenomenon. The weather had been 

 very " thundery" all the morning, and heavy rain was falling in 

 torrents. I sat at my desk by a window looking out upon a 

 court inclosed by high walls. Chancing to look out of the win- 

 dow I heard a sharp report, just dike the crack of a Snider 

 rifle sounding immediately outside, followed instantaneously by 

 the descent of a ball of fire about the size of an ordinary gas- 

 lamp globe. Thio fell vertically and with lightning speed, but 

 when just on a line with the centre of my window burst into 

 a splendid mass of rays, whitish-blue in colour, and of dazzling 

 brilliancy. That is all I can tell you about it. Evei-y one in 

 the house heard the report, and quite a temporary panic ensued. 

 No material effect of the meteorite's presence can be found. 



Perhaps some of your readers may be able to explain Uie phe- 

 nomenon. J. Harris Stone 



67, Cliandos Street, Strand, August 23 



The Australian Monotremes 



The Tachyglossiis was shot by me near Georgetown, in lat. 

 18° S. I have found it inhabiting the porphyritic ranges 

 (Newcastle and Mount Turner) in this locality, where they are 

 rather numerous. In my letter (Nature, vol. xvi. p. 420) I 

 should have written "integumentary" pouch. The Orintho- 

 rhynch2is paradoxus I'saw floating with its bill above water in a 

 lagoon between Georgetown and Normanton, 150 miles v.est of 

 the former town. 



Owing to the noise made by my detachment in riding up, I 

 was unable to capture this specimen, but I do not despair of 

 securing one on my next trip we.-tAr.rJ. I certainly believe the 



Tachyglossus extends throughout the length of the Cape York 

 peninsula on the east, and through the Gregory, Leichhardt, and 

 Cloncurry ranges to the southward and south-westward of 

 Georgetown. Its habit of burrowing beneath rocks precludes 

 the possibility of its occurrence on the Lower Gilbert and 

 Flinders River plains. 



"P. L. S." will find my "notes" on this subject in the Lin- 

 ncean Society's Journal, as I sent them, accompanied by the 

 skull of an adult female, to the Society in March last. 



Georgetown, June I W. E. A. j 



Microphone in Indirect Circuit 



It is not absolutely necessary that the microphone should 

 form part of the direct circuit. It works just as well if con- 

 nected so that, when the carbons are not touching, the whole of 

 the current goes through the telephone. When the carbons are 

 together a small portion will of course leak through them ; upon 

 this leakage depends the rise and fall of tension in the receiver. 

 For some experiments it is even better to work the microphone 

 in this indirect manner, as the circuit always remains closed, 

 and prevents, in a great measure, the jarring noise resulting 

 from a break. Alfred Chiddey 



Bristol Mining School, August 19 



OUR ASTRONOMICAL COLUMN 



The Satellite of Neptune.— We here present in a 

 tabular form the means of determining the approximate 

 position and distance of the satellite of Neptune, with 

 respect to the primary for any time during the months of 

 September and October, or indeed by extending the 

 epochs subjoined, for any time during the present oppo- 

 sition. The argument tc is the distance of the satellite 

 from the ascending node of the orbit upon the earth's 

 equator, and u = 0°, at these Greenwich mean times : — 



Sept. 



The motion of // in one day is 6i°'257, in one hour2°"552, 

 and in one minute o°'0425. Having determined the value 

 of u from these epochs and motions for the proposed time 

 of observation, the angle of position and distance of the 

 satellite from the centre of the planet may be taken from 

 the following table, in which the first and second columns 

 of angles apply to the respective columns of the argu- 

 ment u : — 



The period of revolution of the satellite is 5d. 2ih. 2-74m., 

 and by successive additions of this period the epochs 

 may be continued for November or later. 



As an example of the application of the table, suppose 

 it is desired to know the approximate position of the 

 satellite on September 14 at Greenwich midnight. 

 Strictly the time for aberration should be deducted, 

 which, in minutes, is given by [0-9189] X log. distance of 

 Neptune from the earth— this log. distance being taken 

 from p. 269 of i\iQ Nautical Almanac. In the present 

 case we find 4h. i-9m. to be deducted from i^h., so that 



