On Painting. 31 



From tills principle, that the great difTerence between the 

 temperature of the vapour and air is neceflary for the pror 

 duftion of found, it may be eafily conceived that every thing 

 which tends to augn-^ent the heat of the current of air, and 

 to diminitli that produced by the combuftion of the gas, will 

 tend alfo to weaken or even to annihilate the found of the 

 tube: but tbefe two circumftances are united in a warm 

 chamber filled with people r the current of air, inllead of 

 being cool, is hot, and the quantity of oxygen being there 

 hefs, the heat produced will be of lefs (trength. It needs 

 therefore excite no aftoniflimcnt, that in fuch chambers the 

 experiment does not always fucceed. 



Brugnateili produced founds in tubes merely by the com- 

 buftion of phofphorus. Some philofophers, conceiving that 

 the fonorous etfetls were owing in a peculiar manner to the 

 hydrogen gas, have been induced to infer the prefenceof that 

 fubftance in phofphorus. From what has been faid, is it not 

 more fimple to explain this phnenomenon by the produclion 

 ot the phofphorous acid under the form of vapours, whicli 

 receive a great degree of elafticity fro.n the caloric difengaged 

 ♦luring the comburtion, and the volume of which is foori di- 

 minifbed by the contad of the cold air? We find there the 

 alternate expanfion and contraction necefiary for communi- 

 cating to the air the undulatory motion proper for producing 

 founds. 



Such are tl>e few obfervatlons I have had an opportunity 

 of making on harmonious tubes ', T hope they will prove in 

 fome meafure interelling to thofe particularly engaged with 

 this branch of philofophy, and that they wdl contribute to- 

 wards making them pay attention to tliis curious fad hitherto 

 negleded. 



w, 



V« On Fainting. By Mr. E. Dayes, Painter.. 



Essay V. 



On Invention. 



Then-, t.sld Tnvcnrion, all thy power; Jiirufe-, 

 Gf all ttiy lifters thou the nobklc mufe ; 

 Tliec cv'ry art, thee ev'iT grace infpires, 

 Tiice I'hotbus fills with alt his biij^hteft fires. 



Mason's Fresn'ot. 



E (lioukl never forget that the value -of every art arifes 

 from the degree of mental capacity requifite to its produdtion, 

 and the degree of inllrudion or pleafure refulting therefrom. 



Hence 



