Notes and Memoranda. 399 



NOTES AND MEMORANDA. 



Note on Nitride of Ikon. — It is an ammonium (NFe^ in which iron 

 takes the place of hydrogen (see Poggendorf's Annalen, May, 1865), and is 

 obtained by heating iron in ammoniacal gas ; or, better still — as mentioned in the 

 Int. Obs., p. 811 — by passing ammonia over pure protochloride of iron ; the 

 reactions being NH4O -\- 4 Fe CI = NFe 4 -\- 4 HCl-f-O. The hydrochloric acid thus 

 produced unites with some of the ammonia, forming chloride of ammonium, which 

 escapes. But, with regard to the oxygen, it is most probable that, in certain 

 cases, it forms NFe 4 0, the analogy with ammonium being thus kept up ; that in 

 others it passes off with the chloride of ammonium ; and that in others it unites 

 with hydrogen, which is set free during the complicated decompositions that 

 occur when nitride of iron is formed, on account of the nitride being decomposed 

 even by the temperature required for its production, and still more by a higher ; 

 nitrides containing varying quantities of nitrogen, and mixtures containing vary- 

 ing quantities of nitride and metallic iron being formed. These mixtures, before 

 the researches of Stahlschmidt, were erroneously considered to be different 

 nitrides. 



Extraordinary Flight of Birds. — A lady, dating from Pont de Brieques, 

 near Boulogne, on the 24th Oct., informs us : " While I write, there comes sud- 

 denly a great thick black cloud, accompanied by an extraordinary noise. We 

 are all terrified till we discover the cause. Figure to yourself an innumerable 

 flight of black birds as big as pigeons, and going northwards." Similar flights of 

 birds were seen by M. De la Blanchere in the department of Sarthe, on the 30th 

 Oct. See Comptes JZendus. 



Lunar Photography. — During the partial eclipse of the moon on the 4th 

 Oct., Mr. De la Rue took a series of seventeen photographs, using Steinheil's 

 13-inch silvered glas3 mirror of 10 feet focal length, the action of which he did 

 not find more rapid than that of the speculum metal mirrors of same dimensions 

 and focal length which he had previously employed. This is curious, as the 

 reflective power of the silver film is, according to Sir J. Herschel, to that of the 

 best speculum alloy, as 91 to 67. Mr. De la Rue says — " After contact it was 

 found that while an instantaneous exposure sufficed to give a faint impression of 

 that portion of the lunar disk not obscured by the umbra or penumbra, an ex- 

 posure of a whole minute failed to bring out the details of the lunar surface 

 covered by the umbra, although its details were plainly perceptible in the 

 telescope. The obscured portion of the moon was moreover perfectly visible 

 without optical aid. Further details will be found in Monthly Notices (Supple- 

 mental Notice), No. 9. 



J" Hercules.— In Monthly Notices (Supplemental Notice), No. 9, Mr. 

 Fletcher states that at present this star is absolutely single with his 9f , inch 

 refractor, and power of 1000. A few years ago he had no difficulty in measuring 

 the distance of the companion star with a 4-inch telescope ; and he shews that 

 as the companion is close to its perihelion, the earliest possible observation of its 

 reappearance will be valuable. 



New Growing Slide. — Mr. H. L. Smith, of Kenyon College, U.S., has con- 

 trived a new growing slide for the microscope. It is composed of two glass plates 

 3X2 inches, and about l-25th of an inch thick, separated by strips of the same 

 thickness, and cemented by marine glue. One corner of the upper plate is 

 removed, and a very small hole drilled through the upper plate at one corner of 

 the space, to be covered by a piece of thin glass placed over the object whose 

 growth is to be watched. The slide is filled with water by means of a pipette applied 

 to the open corner, and when the covering glass is placed over the little hole, 

 water slowly oozes through, as it is affected by capillary attraction. By this 

 means an object is kept moist. The cell i3 said to hold water enough for about 

 three days. — Annals Nat. Sist. 



Dimorphism in Mites. — M. Claparede stated at the last meeting of the 

 Societe Helvetique des Sciences Naturelles that dimorphism is found amongst the 



