‘ 
ADDRESS BY PROFESSOR TRAILL, XX1X 
merce are too obvious to require illustration: but perhaps it may not 
be unsuitable, in this place, to refer to the deductions of our eminent 
associate, Captain Denham, on the capability of the Mersey “ to com- 
mand a navigable avenue to the ocean, so long asits guardians preserve 
the high-water boundaries from artificial contraction.” It may also be 
stated, that in our Transactions, this gentleman has recorded his most 
important general inference (drawn from a connected series of observa- 
tions on the tides, which the liberality of the Dock Trustees of Liverpool 
enabled him to carry on)—that there is one invariable mean height, com- 
mon to neap and spring tides—rur Harr Trp—e Marx—a point from 
which engineers, geologists, and navigators will henceforward com- 
mence their calculations, and adjust their standards of comparison. 
The Association made application soon after the meeting at Edin- 
burgh for the resumption of the Trigonometrical Survey of Scotland ; 
a work imperiously demanded by the imperfect state of our best maps 
and charts of that part of the island, either for the purposes of geology 
or navigation. It is needless to give further proof, than that parts of se- 
veral of the large islands at the mouth of the Clyde are laid down se- 
veral miles out of their true position. The magnificent scale on which 
the survey of Ireland is now carrying on, emboldened various scientific 
societies of Scotland this year to memorialize the government on the 
subject. I am happy to add, that the applications have been successful, 
and the triangulation of Scotland will recommence early in 1838. 
The British Association may also boast, that at its instigation, our 
illustrious associate, Arago, moved the Bureau des Longitudes to soli- 
cit from the French government the publication of the series of obser- 
vations on the tides at Brest, and a reduction of the astronomical obser- 
vations made at the Ecole Militaire. The Brest observations have been 
printed, and a copy of the valuable documents put in the hands of one 
well able to appreciate them. 
At the Dublin meeting, a committee was appointed for representing 
to our own government two objects important to science ; which can 
only be accomplished in a satisfactory manner by the rulers of a power- 
ful nation, or by an union of governments in the cause of philosophy. 
The first related to the establishment of Magnetical and Meteorological 
Observatories, in different parts of the earth, furnished with proper in- 
struments, and in which the observations should be conducted on ac- 
_knowledged and uniform principles. The extent, and the variety of 
climate of the British possessions, indicate them as favourable points 
for such establishments, which have already been commenced in France 
and its dependencies, and may hereafter, by the co-operation of the 
