( } 7 ° ) 
They are about 20, and 23 Years old. Qn* whe- 
ther - this may not be accounted for, by fuppofingthe 
Flame to rarify the Air, and make a Sort of V acuum 
about one •, into which when it returns again, it gives 
the Likenefs of a Stroke with a Beetle, as he expref- 
fes it. I fancy a Wind-Gun, with comprefs’d Air, 
wou’d have the fame EfFed, and might eafily be try’d 
upon a Dog, or fuch like Animal. 
IV- T>e Embus Magnet lets. Epijlola Virl DottiJJimi. 
P. Mufchenbroek, M. T>- ad J. Th. 
Defaguliers, LL. T>. 5^. 5. 5. 
Q Uum motus, quos vocamus Attradiones, frequen- 
tiffimi videantur in Natura, 6c plurimi efFedus 
ab hi fee pendeant, ad eos animum advertere caepi, ut 
intelligerem quales dTent, quaenam eorum caufa, 6c 
quibufnam proportion ibus operarentur : cum vero in 
magnetibus videantur hi efFedus fortiffimi, fufpicari 
expi an ex iis non aliquantum plus lucis fasnerarer, 
quam ex aliis corporibus * 6c an, quod in majori gradu 
obtinet inter magnetes, non obtineret in minori for- 
fan inter quaslibet alia corpora \ ad experiments cum 
magnetibus igitur veni, plura diverfa infhtui, quae in- 
fra deferibam, fed pofl plurimos labores videor lllud 
tantum colligere poffe j magnetes non agere in e,. 
aut in ferrum, per effluvia quasdam corporea, fed cau- 
fam eorum efie penitus ignotam, 6c forte non corpo- 
ream. Conjeduris non detinebo te, nec pretiofiffimum, 
ciuod tibi fupereft a gravioribus negotns, furripiam 
hifee vanis cogitationibus tempus ; credo emm nihil 
efTe magis noxium promovendae feientia?, quam 11 con- 
reduras pro demonftrationibus obtrudamus. _ 
' * Prtntnm 
