Mathematical Concfpoiuieiice. ^p 



lamps fupported by inflammable air, appeared to them deferving of a particular examinatioa 

 in confequence of the curious properties it prefented, particularly when compared with the 

 gaffes afforded by alcohol and ether treated by other methods. 



Secondly, From having remarked that the gas is difengaged towards the end of the 

 procefs for making ether, they took the proportions of the mixture which exifls at this 

 period of the etherification ; that is to fay, four parts of concentrated fulphuric acid and 

 one of alcohol, and treated this mixture in a common glafs body appropriated to the pro- 

 duction of aeriform fluids. 



The third paragraph defcribes the feries of plienomena which take place during the pro- 

 duclion of this gas. The mixture heats and becomes brown; gas is extricated without 

 the application of external heat ; but when fuch heat is applied, the elFervefcence great!" 

 increafes, the colour of the mixture becomes black, the gas pafTes abundantly ; it is even 

 neceffary, to prevent the whole of the liquor from quitting the vefTel, that the heat fhould 

 be withdrawn. The refidue, after the extra£lion of the gas, confuts of fulphureous acid 

 mixed with coal, which renders "it black. Citizen Fourcroy remarks, that the defcriptioii 

 makes no mention of ether being produced. 



[To hi concluded in the next Nuinber.l 



MATHEMATICAL CORRESPONDENCE. 



J\S> the prefent Journal is defigned to embrace every branch of ufeful knowledge, both in 

 fcience and the arts, a certain portion of it will be devoted to the infertion of fuch mathe- 

 matical difTcrtations and queflions, as by their novelty or importance appear to deferve the 

 attention of the public. Every communication, therefore, of this kind, directed to the Edi- 

 tor, pofl paid, will be thankfully received, and publilhed as early, in fome of the fucceeding 

 numbers, as the plan of the work will admit ; but it is particularly requefted that the con- 

 tributors of queftions will dired them, as much as pofTible, to pradlical or theoretical im- 

 provement ; as none that are forced, or framed upon obfcure enigmatical principles, which 

 when difcovered are of no value, will be inferted. 



The following QUESTIONS are propofed for Solution. 

 Question I. By J. B. 

 IT is required to divide the half of a given right line into a given number of parts fo that 

 each part, and the fum of that part and the remainder of the whole line may be in geome- 

 trical progreffion ; this being a queftion of praflical utility in the divifion of the monochord 

 or mufical ftiing. 



Question II. By Capt. W. Mvdgf.. 

 IT IS required to determine the centrifugal force of a body moving in the circumference 

 cf a circle, by the pure principles of fluxions, inflead of deriving it from the doftrine of indi- 

 vifiblcs, as is done by Newton in the Principia. 



SCIEN. 



