io6 
Notes and Comments. 
Humber. If Hull missed it, she would also lose the trade 
which the coal vessels brought back, and in that way she 
would gradually be side-tracked. Generally speaking, the 
schemes so far propounded divided themselves between an 
easterly and a westerly route. By the easterly route it was 
proposed to cut a tunnel placing Hull into quicker reach of 
Grimsby, as to which he would only say that if Hull accepted 
this she would deserve to fail, because it would only mean the 
diversion of traffic to Grimsby — a port much nearer the sea. 
Besides, it took little account of geological conditions. He 
showed a plan illustrating the effect of glacial deposits upon 
the coast of Holderness, by which it appeared that in pre- 
glacial times the mouth of the Humber was close to Hull, 
was trumpet-shaped, and pointed due east. Now the river 
debouches to the south-east. An engineer constructing a 
tunnel at this point, therefore, would strike into boulder clay 
and gravel, which was very treacherous and difficult to work. 
He would, in fact, meet with the same fate as the first pro- 
jectors of the first tunnel at Liverpool for the Yyrnwy Water- 
works. Personally, he was in favour of a tunnel on the west 
side of Hull, because it would avoid the boulder clay and 
would serve Hull better. No easier ground for the purpose 
could be found in the kingdom. 
MACADAM ROADS. 
Professor Fearnsides had a paper ‘ On the part played by 
water in Macadam road construction,’ in The Quarry, for 
February and March. He concludes that (i) The chemical 
action of water upon materials in roads is small as compared 
with the rate of mechanical wear ; but care should be exercised 
in choosing materials which are to be buried in road founda- 
tions. Furnace slag for this purpose is not above suspicion. 
(2) The power of water to bind is an effect of surface tension, 
and for maximum strength and efficiency it is important 
that the proportion of water should be kept at the optimum ; 
‘ as dry as it can be drained ’ is the first approximation to 
the optimum for most water-bound road materials. Pot- 
holes grow by wear of traffic at those places where by local 
water-pockets the proportion of water is kept above the opti- 
mum. 
AND WATER. 
(3) Certain site-rocks, the argillaceous or clay rocks, 
owe their strength to waterbinding, and are subject to the 
same conditions of optimum water-content. The importance 
of cambering and draining the site is therefore equal to that 
of arranging the configuration of the road surface. (4) The 
effects of dew, more especially the dew which distils from 
Naturalist, 
