^{page 268 note *} That others have noticed the occurrence of this seaweed in polluted sea water, and the nuisance which may arise from it, is shown by the following letter which we received from Professor Hartley, F.R.S., of the Royal College of Science, Dublin, during our investigation on the subject:—

“Professor Johnson has shown me your letter in re the sewage of Belfast and the shore weed. That weed is never seen on any shore unless sewage runs into the water. The stronger the sewage and the greater its volume, the more luxuriant its growth. I have observed this during the last twenty years in England, Wales, Ireland, and Scotland. About eight years ago I washed some of the weed in fresh sea water and placed it in a bottle of the same. In about twenty-four hours the bottle was opened and the contents found to be in an exceedingly offensive state.

“A paper of mine in the Proc. Ro-y. Soc. Edinburgh, session 1895–96, touches upon this matter.”

Nothing, however, appears to have been published on the subject, and we are under the impression that most botanists consider Ulva latissima as characteristic rather of brackish than of polluted sea water.

^{page 269 note *} The weed, as obtained by us from the Belfast foreshore, was nearly always infested with minute spiral shell-fish, which feed upon it and eat out circular holes.

^{page 271 note *} The gas remaining after explosion contained no CO₂.

^{page 284 note *} Zelinsky, , Proceedings of the Russian Physical and Chemical Society, 25, fasc. 5 [1893].Google Scholar

^{page 286 note *} Thorpe's Diet. Appl. Chem.

^{page 286 note †} Würtz, Dict. d. Chim.