68 Sckntific tnteUigenc$* Vv^yt 



11. Diurnal Variation of the Magnetic Needle, 



We understand that Mr. Christie has continued to pursue his inqui- 

 ries on this subject, as noticed in our report of Mr. Barlow's paper, 

 and that he has been led to conclude from them, that it is the calorific 

 and not the colorific rays that produce the change in question. He 

 has found that a change of temperature in his opposing magnets, to the 

 amount of one degree only, will produce a change of nearly a degree 

 in the direction of the needle. He showed by the most satisfactory 

 experiments, before Professors Oersted and Barlow, that the mere 

 change of heat produced by applying his hand to the magnet, when 

 the needle was thus nicely adjusted, caused a deviation to the amount 

 of between two and three degrees. 



Mr. Christie has communicated the first P^'t of his experiments to 

 the Royal Society, as announced in our report of the final proceedings 

 of that body for the present Session. 



HI. Frauds and Impeifidions in Paper-making. 



In order to increase the weight of printing papers, some manufactu^ 

 rcrs are in the habit of mixing sulphate of lime or gypsum with the 

 rags to a great extent. I have been informed by authority, upon which 

 I place great reliance, that some paper contains more than one-fourth 

 of its weight of gypsum ; and I lately examined a sample which had the 

 appearance of a good paper that contained about 12 per cent. 



The mode of detecting this fraud is extremely simple : Burn 100 

 grains, or any given weight of the paper in a platina, or earthern cruci- 

 ble, and continue the heat until the residuum becomes white, which 

 it will readily do if the paper is mixed with gypsum. It is certainly true 

 that all paper contains a small quantity of incombustible matter derived 

 from accidental impurities, but it does not amount to more than about 

 one per cent. ; the weight then will indicate the extent of the fraud. 



With respect to the imperfection of paper, I allude to the slovenly 

 mode in which the bleaching by means of chlorine or oxymuriatic acid 

 is effected. This, after its operation, is frequently left in such quan- 

 tity in the paper that it may be readily detected by the smell. Some- 

 time since, a button-maker in Birmingham, who had manufactured the 

 buttons in the usual way, was surprised to find that after being a short 

 time kept, they were so tarnished as to be unsaleable; on searching for the 

 cause, he found that it was derived from the action of the chlorine 

 which had been left in the paper to such an extent a^ to act upon the 

 metallic buttons. — Edit, 



IV. Boiling Spring of Mile. 



The 14th volume of the AnnaU, p. 27, contains an analysis of the 

 water of the boiling springs of Milo ; but this island is there incorrectly 

 called Milto. Tor this correction I am indebted to the Rev. Mr. 

 Holme, of Cambridge, by whom the water was supplied for analysis. 

 --Edit. 



V. Cri/stals formed in Solution of Cyanogen. 

 M. Vauquelin observed tliat a strong solution of cyanogen which he 

 kept in his laboratory during the winter, became in about four months of 



