156 An Address in Commemoration of J. W. Bai 
across the Atlantic, made in reference to the laying of the tele: 
graphic cable, occupied his attention. In pursuing these exam- 
inations, he found the relics from the bottom so well characterized 
in certain localities and at certain depths, that he suggested the 
possibility of being able, in some instances at least, to determine 
the safety or otherwise of a vessel, by an examination of the 
few among us have ventured upon the purchase of a valuable 
instrument, without first consulting him in reference to it, and ~ 
perhaps taxing him with unwelcome negotiations; and his letters 
show that numerous applications of this kind m e been a 
most serious tax upon his time. It is said that his own early — 
observations were made with globules of glass blown by himself. 
_ After he became possessed of a proper instrument, many modi: 
fications in the construction of the stage and its movements, 
and in other appendages, were made by him; and it is to his 
experience and scientific deductions, coupled with the genius 
and incomparable optical skill of Spencer, that we are indebted 
_ for the most powerful microscopes that have yet been made. 
Px. is masterly and triumphant defense of them against the de- 
__ tractions of transatlantic pens, also exhibits his complete mastery 
of the subject. One of his last essays was to construct an Ind 
cator, by means of which the place of any object on a si 
might readily and certainly be found. No one, in looking at tl 
eard, would credit the labor and thought which he, in con) 
ton with his friends, Judge Johnson and Mr. Gavitt, bestow! 
uponat. Many futile efforts were made, and many quires we 
‘ Sed'm correspondence, before the accuracy of its measuremen 
_ anda method for the unerring application of it, were satisfact 
= 
~ 
