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Proceedings of the Royal Society 
more intense than gravity, and one which, unlike gravity, depends 
on the quality as well as the quantity of matter. It seems to the 
author that the introduction of such hypotheses is inconsistent with 
Newton's “ Regulse Philosophandi ” until it is definitely proved (as 
has certainly not yet been done) that known forces are not com- 
petent to produce the observed results. 
5. Additional Observations on Fungus Disease of Salmon 
and other Fish. By A. B. Stirling, Assistant-Curator 
in the Museum of Anatomy in the University of Edin- 
burgh. Communicated by Prof. Turner. 
In a paper read to the Society in June last, “ Proceedings,” June 
1879, on the fungus disease affecting salmon and other fish, I dis- 
cussed the various theories which were advocated, as to the cause of 
the disease ; the effects of the fungus upon the fish, the vegetative 
and reproductive aspects of the fungus, and the belief that salt water 
had a curative effect upon salmon affected with fungus disease, on 
their reaching and remaining for some time in that element. 
I also mentioned that at the instance of the Tweed Commissioners, 
an experiment was being conducted by G. H. Fist, Esq.,, to test 
whether that belief was well founded. I will now state the nature 
and result of the experiment, and afterwards relate to the Society, 
an account of an epidemic of fungus, which occurred at Ightham 
Mote, in the county of Kent in 1874, and which appeared again in 
a virulent form a few weeks ago. 
The experiment referred to was conducted as follows : — A wooden 
cage, large enough to allow a salmon to move about within it, and 
perforated with holes so as to allow the water to flow freely through 
it, was prepared. It was then moored in the tideway in the River 
Tweed, below Berwick bridge, where the water is at all times more 
or less salt, and was now ready to receive a fish for experiment. 
About the end of May last a sea-trout kelt was captured at 
Eithermouth, three miles up the river, and within the influence of 
the tide. It was placed in a suitable vessel and conveyed to 
Berwick, where it was enclosed in the cage. The fish is stated by 
Mr List to have been affected with a sloughing sore on the top of 
the head from the point of the snout about two inches in length and 
