Miscellaneous Intelligence. 129 



5. On the Existence of the Color Brown; by Ernest Brucke. 

 (From PoggendorfFs Annalen, No. 7, 1848, having been read before 

 the Physical Society of Berlin on the 23d of June, 1848; Phil. Mag., 

 xxxiii, 281.) — Brown is wanting in the prismatic spectrum, and its re- 

 lation to the colors of the spectrum is as yet unknown. Any one 

 may, however, easily convince himself that brown is nothing more than 

 the complementary color to that of Herschel's lavender-gray rays, 

 t. e. white light from which these rays have been removed. 



For this purpose, separate plates should be split from crystallized 

 gypsum in such a manner that on one side they are as thin as possible, 

 and from it gradually increase in thickness in broad terraces. One of 

 these plates is placed under the microscope, which must be furnished 

 with two Nichol's prisms, one beneath the object-glass, and one in the 

 eye-piece, and so arranged, the prisms being parallel, and the linear 

 magnifying power being about twenty diameters (at a distance of eight 

 French inches), that the above-mentioned thin side is in the field. If 

 it is sufficiently thin, no color is perceived immediately at the side ; 

 but as we proceed towards the thicker part, at first a pale brown tint 

 becomes visible, as if we were looking through a very thin plate of 

 horn, and as the thickness of the plate gradually increases in broad and 

 low terraces, the brown continues to become darker until it assumes a 

 deep and pure nut-brown color, without the intervention of any of the 

 prismatic colors which the thicker parts of the plate exhibit. 



It is evident that the plate at the margin where it appears colorless 

 ls so thin, that the difference of the path of the ordinary and extraor- 

 dinary ray on their exit does not amount to half the length of a wave 

 for any ctflor. Thus interference of the most refractive rays does 

 not occur until the thickness is greater, and the brown color must 

 therefore be produced by the disappearance of the lavender-gray rays 

 from the compound light. 



The correctness of this conclusion is readily tested. On crossing the 

 Prisms, it is seen that whilst in the case of ail the other colors of the 

 plate the well-known complementary colors appear, that portion 

 which was previously brown becomes colored lavender-gray, and tthe 

 intensity of this color is in proportion to the depth of the brown pre- 

 viously observed at the same spot. 



6. Inundation of the Indus. Taken from the lips of an Eye-wit- 

 ness in a. d. 1842. Communicated by Captain J. Abbott, (Jameson's- 

 J our., Oct., 1848, xlv, p. 393. Journal of the Asiatic Society of Ben 



gal. New series, No. 188, p. 230.)— Ushruff Khan, Zemindar of Tor- 

 baila, states, — " In the month of Poos (December), the Indus was very 

 low. I n jy[ aag and phagoon (January and February), it was so low as 

 to be fordable (an unprecedented phenomenon). In Chayt, it contin- 

 ued very low, but not fordable. In Bysakh (April) the same. About 

 the middle of Jayt (May), the atmosphere was one day observed to be 

 Ve ry thick, the air still. At about 2 p. m., a murmuring sound was heard 

 from the northeast, amongst the mountains, which increased until it at- 

 tracted universal attention", and we began to exclaim, ■ What is this mur. 

 ™ u r i Is it the sound of cannon in the distance ? Is Gundgurh bellowing ? 

 Is »t thunder ? 1 Suddenly some cried out, l The rivers come P and I look- 

 ed and perceived that all the dry channels were already filled, and that 



■% Second Series, Vol. VII 7 No. Jl).— Jan., 1849. 17 



