Mifcelhnea Curiofa. 131 



And all that I have fpoken of Vifion holds true 

 of Hearing alfo, both and Reflex*, and 



therefore need not be repeated, 



grafted Vifion arifes from the different Den- 

 fi*?* F >gure, and Magnitude of the Medium, 

 which is fomewhatalter'd alfo by the direrfe m- 

 cidenee of the vifible Rays. And fo it is in 

 M rafted Hearing, all theft Caufes concur to 

 its Produ&ion, and fbme others to be hereafter 

 confidercj. 



Now as any Object (a Man for example) feen 

 through a thicken'd Air, by {{efraftion appears 

 greater than really he is : So iikewife a Sound, 

 heard through the fame thicken'd part of the 

 Atmofphere, will be confiderably vary'd from 

 What it would feem to be, if heard through a 

 thinner Medium. 



And this I call a grafted Sound : But what 

 this Refraction of Sound is, and how caus'cL 

 may hereafter be difcufs'd, when the Nature, 

 and Motion, or Progreffion of Sounds are well 

 ftated. 



For the Improvement of Mr aft ed Vifion ^ 

 tincial Inftruments have been made, by grinding 

 or blowing GlafTes, into a cerrain Figure, and 

 placing them at due diftances, whereby the Ob- 

 ject may be (as 'twere) enabled to fend forth 

 its Rays more vigoroufly, and the Vifive Fa- 

 culty impowerM the better to receive them 

 And thus alfo Inftruments may be contriv'd for 

 the affixing both the Sonorous Body, to fend 

 torch its Sound more ftrongly, and the Acou- 

 fiscK Vacuity, to receive and difcern it more eafily 

 and clearly. For, * 

 1 . As a fine Glafs Bubble, fill'd with clear Wa£ 

 ft and . P la f <J before a burning Candle or 

 Ump, does help it to dart forth its Rays to a 

 ^ z prodigious 



