jjjo S:li'tki'i of Pko/phcnis. — Gtintit^s Rule. 



and have been fufed by caloric (Exp. V. VI. and VllL). The air of the »tmofphcre dif- 

 folves phol'pJiorus at the moment it burns it, and the folution is fenfibly phofphorcfccnt 

 when the experiment is made in a cryftal glafs bottle. This caufes a flame more or lefs 

 brilliant, in proportion to tJie greater or Icfs quantity of phofphorus which is burned at 

 the fame time. 



6. Phofphorus which is burned in a decanter with water at the bottom, not only de* 

 compofcs the oxygcnc of the air in which it burns, but likewife that of the air which is 

 found mixed with water {Exp. X). 



•J. Oil of turpentine and oil of thyme, containinc; phofphorus, do not burn in contaiSl: 

 with atmofpheric air at the ordinary temperature (Exp. XL). 



8. Alkohol difiblves phofphorus, and lofes its agreeable fmell. Phofphorus fliines in 

 the atmofpheric air of clofed velTels, by pouring phofphorated alkohol upon fomejubftance 

 which fhall combine with the liquid and feparate the phofphorus ; fuch are water, ful- 

 phuric acid, &c. (Exp. XII. XIII. XIF.) 



Sulphuric ether likewife diflblves phofphonis, and this folution is not decompofed by 

 water, upon which it floats ; but when phofphorated ether is diluted with alkohol, 

 or is changed into anodyne liquor, it then combines with water, and quits the phof- 

 phorus, which, being divided into very fine white panicles, gives the mixture the colour 

 of milk. 



IV. 



On the Advantage of inverting the Slider in many Operation! on the Common Sliding Rul(. 



By the Rev. W. PSARSON, of Lincoln. 



To Mr. Nicholson, Author of the " Journal of Natural Philofophy" i^c. 



SIR, - 



O 



' N perufing the eighth number of your Journal, I was much pleafed with the ingeni- 

 ous inftruments mentioned in the Vlllth article, upon which the graduations of Gunter's 

 Line of Numbers arc fo difpofed as to be very confider.ibly enlarged, whilfl: yet the whole 

 range of a fingle line is contained in a fmall compafs. If an inllrument of either the pa- 

 rallel, circular, or fpiral confiruiSlion, of a convenient fize, were manufa£lured for fale, with 

 a proper degree of accuracy, I am fully perfuaded that confidcrable advantage-iwould be 

 derived therefrom by purchafers ; particularly by thofe perfons whofe profclTion is to make 

 prafllcal calculations. But as the public are in pofleflion of a Hiding rule, in the operations 

 of which long ufage has made every mechanic expert, it is to be apprehended that pre- 

 judice would in this, as ii» other inftances, prove an obflaclc to the general faie of fuch an 

 inftrument, were the introduction of one into general ufe attempted. This obfervation is, 

 1 believe, verified by the flow fale of the patent, and alfo of the new improved Hiding rule, 

 in comparifon of that of the common one, amongft artificers, who conlUtute the moft 

 numerous clafs of purchafers. I have been informed by a reputabK tradefjnan, who retails 

 Aiding rules of the different conflruiflions, that for every patent, or new improved Hiding 

 rule that is purchafed, more than twenty of Cogfliall's, or tlie common Aiding rules, are 



fold. 



