i 
of measuring Time ai Sea. » 4} 
ages it has been the principal object of their researches, as 
well as of astronomers and philosophers of the greatest ce- 
lebrity. In the second place, by the expression ‘* fo deter- 
mine,” the academy appears to require also palpable proofs 
that the method proposed is the best possible. 
To comply with these requests I shall divide this memoir 
into four parts. 
In the first I shall go through the different methods hi- 
therto attempted, or which may be hereafter tried, for mea- 
suring time at sea; I shall make known the insufficiency of 
most of these methods; and I shall show that, notwithstand- 
ing the irregularities of our portable watches, we are tho- 
roughly persuaded that the best means of obtaining the 
desired measure of time consists in a kind of perfected 
watch. 
In the second part J will endeavour to point out all these 
irregularities, and to discover the different causes, physical 
or mechanical, whence they are derived, in order to be more 
in a state to correct them afterwards. 
_ The third shall contain the description of a chronometer, 
or kind of large watch, deposited with this memoir. TI shall 
show that by its construction it is exempt from the defects 
remarked in common watches, and | shall enter into the 
detail of the expedients which have. becn used in the work- 
manship to prevent them. 
Lastly, I shall terminate this memoir by a recapitulation 
or suite of observations, forming so many parallels to the 
methods which I have employed, with those that may be 
made use of with the same view. I hope to prove, by ex- 
periments and palpable reasonings, that mine must obtain 
the preference. If I succeed, I shall be well paid for twenty 
years consumed in these researches; since, besides the ho- 
nour of being crowned by the Academy of Sciences, this 
discovery concerns the good of humanity, and even the 
preservation of a number of lives. If, on the contrary, 
my labour is without success, there will remain at least the 
satisfaction of having spared no pains or expense i endea- 
vouring to fulfil the bonourabte task imposed upon me as a 
man, a patriot, and an artist. ‘ 
Part 
