14 
THE BRITISH ASSOCIATION AT CARDIFF. 
Jan., 1892 
I now come to what is supposed to be the more immediate 
business of the Association, that is, its indoor meetings. 
The proceedings were commenced, as you have probably 
seen, by an address by Dr. Huggins, its president. His 
subject was the branch of astronomy to which his labours 
have chiefly been devoted, namely, the spectroscopic 
examination of the stars. I am saved, however, the 
necessity of reporting it to you, by the fact that Sir B. 
Ball, in his recent address to the Midland Institute, dwelt 
upon precisely those points which struck me in Dr. Huggins’ 
address. It is the custom at the meetings of the Association 
to decorate the reception room with banners appropriate to 
each of its past meetings. You will see among the photos 
a copy of the one prepared by Dr. Huggins this year. At the 
top of it there is a stripe which, on the banner, was worked 
with the colours of the spectrum, and beneath is the glorious 
constellation of Orion and the Dogstar. 
The first general lecture to the members was given by 
Prof. Miall, on “ Certain Difficulties in the Life of Aquatic 
Insects.” The lecture was admirably illustrated. I was 
particularly struck by the way in which troughs containing 
living insects were shown right way up on the screen. This 
was done by sending the light obliquely downwards through 
the object, and then reflecting it up again on to the screen, 
by means of a totally reflecting prism. The most interesting 
point of the lecture, to me, was the influence of the surface 
tension of water. By this expression is meant that the 
molecules forming the surface of a liquid in contact with air 
have different properties to those in the body of it. and that 
they act as though there were upon it an elastic film which 
resists the passage of the body into or out of the liquid, 
according to whether the body repels or attracts the liquid. 
By this I do not mean that there is any foreign substance 
forming a scum over the liquid; in fact, any greasy or other 
impurity will always lessen the surface tension of water. 
It is unnecessary for me to shew you that light bodies 
will rest on water, though specifically heavier, provided 
that they do not become wetted. Thus a polished steel 
needle will float on water in a sort of trough formed under 
it, and there are several insects which may be seen on 
almost any calm sheet of water skating about with the 
utmost facility. This appears to be due to the quantity of 
hair on their legs, and Professor Miall gave the following 
illustration : If you press a sheet of paper down on a 
sharp point it will be penetrated, but if you imagine an 
exceedingly great number of points, there will be required 
