OhiUiary Notices. 
Ixxvii 
erection of works exposed to heavy seas in deep water. He 
devoted special care to ascertain the force, height, and laws of the 
propagation of sea waves, and their action on artificial structures. 
The measurement of the force of the waves was carried out with 
some degree of completeness by means of instruments which he 
devised, such as the Marine Dynamometer. The result of his 
wave observations, and the laws he deduced from them, were 
given in papers communicated to this Society, to the Edinburgh 
Philosophical Journal, and also in his book on Harbours. In 
1852, after a series of experiments, he enunciated the law of 
the increase of the height of waves in relation to “fetch” ; other 
experiments led to formulae involving the relations between the 
heights of waves and the various influences which modify them, 
and also to formulae by which the reductive powers of harbours 
and breakwaters — or their power of reducing the height of waves 
after passing within the entrance — could he calculated, all of 
which are of great value to the marine engineer. He always held, 
however, that much remained to be done, especially in ascertain- 
ing facts, and he considered his own work in this direction as only 
approximations. More than thirty years ago he was invited to 
write the article “Harbours” for the Encyelopcedia Britannica, 
which was subsequently published as a separate treatise on The 
Design and Construction of Harbours, and it is now in its third 
edition. 
He came of a well-known family of engineers, all of whom have 
been highly distinguished in their profession; and his nephew, 
David Alan Stevenson, was conjoined with him in the engineership 
of the Scottish lighthouses on his father’s resignation, and is now 
the Engineer of the Board, being the fifth in succession in that office. 
He was elected a Fellow of this Society in 1848, acted as a 
member of Council, as one of its Vice-Presidents, and in 1885 
was elected its President. He frequently contributed to our Pro- 
ceedings. He was elected a Member of the Institution of Civil 
Engineers in 1864 ; and one of his last literary works was a lecture 
on “Tides and Coast Works,” which he prepared at the request of 
the Council of that Institution, hut which, owing to ill health, he 
was unable to read. He was a Fellow of the Society of Antiquaries 
of Scotland, the Geological, and other Societies. 
