56 SCIENTIFIC NEWS. 



SCIENTIFIC NEWS, few 



Experiment of the Invifible Girl, 

 Defcnption of jV[oNS. Charles, brother to the well known philofopher of 



the apparatus for r r . . . . * * 



the experiment that name, has tor lome time exhibited in Leiceiter-iquare an 

 of the Invifible experiment called the Invifible Girl, which feems to include 

 lome principle of acouftics either newly difcovered, or not hi- 

 therto known to the extent there difplayed. In the middle of 

 a large lofty room in an old houfe, where from the appearance 

 of the wainfcot, the pofition of fome glafs cafes of natural hif- 

 tory that occupy one fide, and from other circumftances, there 

 does not appear to be any (ituation for acouttic tubes or re- 

 flectors-— is fixed a wooden railing about four feet high, and 

 five feet wide, inclofing a fquare fpace. From the four cor- 

 ner ports of this railing there rife painted wires, or rods, to an 

 eminence of ten or twelve feet, (the cieling being much lof- 

 tier) and from the upper ends of thefe hangs, by firings refem- 

 bling the lines ufed with curtains, a fquare glazed box, having 

 a mahogany bottom nearly on a level with the top of the rail- 

 ing, and in the middle of this box is fufpended an hemifphere 

 (or larger portion) of tin or pewter, out of which proceed ho- 

 rizontally four tin trumpets at right angles to each other, and 

 about eighteen inches long. The dilk or hemifphere is covered 

 with a portion of a quickfilvered glafs globe which completes 

 the fphere, and clofes it imperfectly, fo as not to prevent the 

 inner aperture of one of the trumpets from being feen through 

 the place of infertion. This whole apparatus is fo far de- 

 tached from all furrounding objects, that it can be fwung about 

 as far as the railing will allow ; that is to fay, the box can be 

 fwung by its four firings, and the. globe and trumpets by the 

 firing that fuilains them in the box. The globe may be about 

 ten inches in diameter. In all thefe dimenfions, which I do 

 not fuppofe to be material, I fpeak from the recollection of fome 

 weeks ago. 

 Manner in In the exhibition, the Invifible Girl is fuppofed or pretended 



ir^es h fro h mthL Cefol3einclude<:l in the f P here ' and the convention is held by 



apparatus. fpeaking into any one of the trumpets, and the reply comes 



out of them ; that is to fay, it is mod clearly heard by applying 



the ear to one of their mouths. The voice is low, as if con- 



yey«d 



