The Colour of Sea Water

Abstract

AS Mr. Threlfall, in his letter to NATURE of March 16, seems to have fallen into an error regarding the explanation of the colour of sea water, given by me in the paper referred to in his letter, perhaps I may be allowed to make a few remarks on the subject, He says my explanation is based on the principle that sea water is a blue liquid, and that the green tint often seen in sea water is due to the presence of yellow particles. Now, while it is pointed out in the paper referred to that yellow particles will make a blue water appear greenish, yet it is nowhere stated that yellow particles are the exclusive cause of greenness in sea waters. What may have caused Mr. Threlfall to make this overlook, may be the fact that only an abstract of the paper was published, and the different points, therefore, not fully explained. Still, I think there is enough in the abstract to show that greenness in sea water was recognised to be due in some cases to other causes than the one referred to in Mr. Threlfall's letter.