Intelligence and Miscellaneous Articles. 481 



readers of the Philosophical Magazine, you will oblige me by making 

 it known. 1 was led to employ this method in consequence of an 

 injury done to a lens, for the regrinding of which I had no corre- 

 sponding brass tool. Rather than take the trouble of making a set 

 of brass gauges and also a set of grinding-tools, I took a cast of the 

 lens itself by pressure upon the cooling surface of some fusible metal 

 contained in a frame of card. On this tool, thus readily formed, I 

 reground and polished the lens ; and where great accuracy of figure 

 is not required, have found the method to answer very well. Hoping 

 that this plan may be useful to others who may meet with a similar 

 casualty, I communicate it. Perhaps I may also be allowed to men- 

 tion, that I have found zinc exceedingly useful for the formation of 

 ordinary grinding-tools, being readily cast and turned ; and though 

 not equal to brass, yet being in many respects superior to the soft 

 metal tools sometimes employed. 



I am, Gentlemen, 



Respectfully yours, 



N. S. Heineken. 



DR. BIALLOBLOTZKY S JOUIINEY TO THE SOURCES OF THE NILE. 



Letters have been received by Dr. Beke from Dr. Bialloblotzky, 

 whose intended exploratory journey into Eastern Africa was noticed 

 in the last Number of the Philosophical Magazine*, by which letters 

 that traveller's proceedings are brought down to the 8th of Novem- 

 ber, when he was at Alexandria. 



Before Dr. Bialloblotzky quitted Vienna on the 7th of October, 

 the Imperial Academy of Sciences granted him the use of some valu- 

 able instruments made by M. Kapeller of Gumpendorf and selected 

 by M. Schaubl of the Imperial Observatory, and the Government 

 procured for him and his son a passage gratis from Vienna to Trieste 

 by the railway, and from Trieste to Athens, Syra and Alexandria, 

 by the steamers of the Austrian Lloyd's. 



It was his intention to quit Suez for Aden on the 23rd of No- 

 vember by the East India Company's steam-packet, by which a free 

 passage has been granted to him by the Court of Directors. 



ON THE ARSENITES OF IRON. 



M. Filhol made a few experiments on the arsenites of iron with 

 the view of discovering a certain method of ascertaining the state in 

 which arsenic exists in chalybeate waters and the deposits which they 

 form ; the author states that he did not find what he looked for, 

 but still he observed some facts which he deemed not unimportant. 



Arsenic does not always exist in chalybeate waters in the state 

 either of arsenite or arseniate, and its presence in certain ferruginous 

 deposits may not be recognized, on account of the state in which it 

 exists. 



In proceeding to analyse a deposit from a spring at a little distance 



* See page 399. 



