214 On the Popular Weather Prognostics of Scotland. 
facilitates the testing of their trustworthiness by careful and 
methodical observation. 
IT. By having them collected together, we are better able 
to compare and generalize. 
In the effort to attain this object, we may find that 
phenomena, which are apparently unconnected, but which 
foretell the same change, are in reality allied through a 
common cause ; we may discover how it happens that certain 
classes of phenomena come to predict certain approaching 
conditions of the weather ; and further, it may happen that 
while sifting well-established popular beliefs, we may fall 
on the proof of important weather laws. 
I shall illustrate my meaning, and at the same time show 
how such an inquiry may become interesting and valuable, 
both in a scientific and practical sense, by reference to the 
following prognostics :— 
A heavy in-shore swell during calm weather is believed 
to foretell wind. This prognostic has been found to be very 
generally correct. The swell, in fact, is merely the product 
of a distant storm then existing, which is travelling towards 
us, and which will probably, though not certainly, reach us. 
The log-books of ships have satisfactorily established the 
truth of this explanation. We are led, therefore, to con- 
clude that storms do not always travel so fast as does their 
influence on the water ; nor is this the only important con- 
clusion concerning the progress of storms which flows from 
the examination of this single phenomenon. 
Again, when the fisherman of the Dornoch Coast, on a 
clear and calm night, hears the sound of rushing waters over 
the Gizzen-Briggs, he expects a storm from the east. Now, 
it is more than probable that this sound is merely another 
manifestation of the precursory swell of which I have just 
been speaking, and which causes it by producing broken 
waters on the sandbank at the mouth of the firth. We 
have here an illustration of how phenomena seemingly un- — 
connected may possibly be due to the same cause. The 
“ebb and flow and ebb again,” near high or low water mark, 
in narrow firths, a phenomenon which fishermen call leakves, 
may also have the same explanation, viz., the action on the 
water of a remote storm, perceived before the arrival of the — 
