L %77 3 
III. A Letter to the Reverend John Theoph. 
Defaguiliers, L. L. T>. F. R. $. from Mr. 
Martin Triewald, F. R. S. Captain Of Me- 
chanics, an d Military Architect to his 
Swedifli Majesty, concerning an Improve* 
ment of the Diving Bell. 
Stockholm , Nov. i. 1732* 
Reverend SIR , 
H A V I N G the foie Privilege for diving on all the 
Coafts in the Baltic belonging to his Swedijh 
Majefty, no Opportunity has been wanting to make 
fufficient Trials with the Diving Bell and Air Barrels 
in feveral Depths, according to the ingenious Im- 
provement of that worthy Gentleman Dr. Edmund 
Halley , made in the Year 1716, but with fomefmali 
Additions. 
Experience has likewife convinc'd me, that no In- 
vention built upon any other Principles than thofe of 
th z Camp ana Urinatoria , can be of Ufe in any con- 
liderable Depths; or that the Diver, in any other In- 
vention whatever, can be a lingle Moment fafe. I 
will not, for Brevity- fake, mention the many Impe- 
diments that attend other Inventions, only that-t>f a 
Water Armour, in which the Man is drowned in an 
Inftant, when fuch a Machine receives the leaft Leak : 
Whereas Experience has fhewn, that when fuch an 
Accident has happen'd to the Diving Bell, as to my 
Knowledge it did once, when the Diver was 1 2 Fa- 
Ccc thorn 
