f 155 ] 
in the open Air : I earned a young Man to dive 
fome Feet down, and then to endeavour to halloo, 
which he did; and I could hear him, though very 
faintly. But imagining the Sound might come up 
with the Water he difeharged at his Mouth whilft 
he halloo’d, 1 contrived a kind of Hand -Granado, 
which I threw into a Place in the River about nine 
Feet deep. The Fuzee burnt underWater near 10 
Seconds, and then the Granado went off, giving a 
prodigious hollow Sound, and fhaking the adjacent 
Ground to fuch a Degree, that the Whole of a large 
Building, fome Yards diftant from the Explofion, was 
put into a Tremor, far beyond what could be ex- 
pected from fo fmall a Quantity of Powder. 
I fatisfied my third Inquiry, Whether, and in what 
Manner, Sound made under Water can be heard by 
a Land Animal that is likewife under Water, by pro- 
curing a young Man to dive down with a Bell in 
his Hand j and he allured me, that he heard its tink- 
ling very diftinCtly, at all Depths under Water, with 
little or no Difference from what he did when rung 
in the open Air: He likewife affirmed, that he 
plainly heard the Noife and Rufhing of the Water, 
which came violently through a Flood-Gate, about 
20 Feet diftant from the Place he then was in. 
If thefe Experiments and Obfervations may be 
thought deferving Notice, I fhall think my Time 
not thrown away ; but at all Events be allured, 
that I am, 
‘Dear Sir, 
Norwich , Nov, 27. 
I 747. Tour mo ft obliged humble Servant , 
W. Arderon. 
X V. 
