74 Scientific Intelligence. [July, 



Where a great excess of hydrogen is used, the experiments of 

 Saussure show that a little ammonia is always formed ; a conden- 

 sation will thus take place greater than what is to be attributed 

 to the action of oxygen. The presence of aqueous vapour will 

 also be a source of fallacy ; on the whole, 1 think, that the small 

 scale on which experiments with Volta's eudiometer are neces- 

 sarily made should lead to the employment of precautions not 

 heretofore deemed requisite. 



Has the result of the comparison between the English and 

 French weights been as yet made public ? E. W. H. R. 



XL Diurnal Variation of lhe Magnetic Needle. 



The readers of the Annals of Philosophy are acquainted with 

 the important series of observations on the diurnal variation of 

 the needle, which Col. Beaufoy has made for more than two 

 years, and which have been regularly published in the Annals. 

 These observations have been hitherto quite unique ; but those 

 who are interested in this intricate but most important investiga- 

 tion will learn with pleasure that measures have been taken for 

 making a similar set of observations in the Paris observatory. By 

 the care also and at the expence of the Marechal Due de Ragusa, 

 an excellent compass, made by Gambey, has been placed at 

 Chatillon-sur-Seine, in Burgundy. In the absence of the Mar- 

 shall, the observations are made by an intelligent and well- 

 informed young man, who has the superintendence of the fine 

 agricultural establishments so much admired around the chateau 

 de Chatillon. — (Ann. de Chim. et de Phys. x. 121.) 



XII. Derangement of the Operations of delicate Balances by 



Electricity. 



The common method of mounting delicate balances with 

 lacquered pans and silk threads is liable to a very serious 

 objection, as the pans eveiy time they are cleaned (espe- 

 cially if a silk handkerchief be employed) are rendered liable 

 to be charged with electricity, and consequently to be at- 

 tracted by contiguous objects. This circumstance has doubt- 

 less been observed, though the author of the present notice 

 has reason to believe that it is not so generally known as 

 it deserves to be. He was led to notice it from possessing 

 a balance mounted in the above manner, the irregularity of 

 the action of which he was for a long time unable to account 

 for, but at length traced it to the circumstance mentioned. It 

 need scarcely be observed, that to obviate such a source of 

 error, the pans and mounting of balances should be made of 

 unvarnished metal, as, for example, of platinum. 



XIII. Prize Questions firoposed bxj the Royal Academr/ of Sciences 



of France for 1821/ 



^No complete memoir having been received by the Academy on 



