ALLOW us to correct a slight error in the address of the President of the Royal Society, as reported in NATURE last week. He speaks of the “completion” of the “Lepidoptera of Ceylon” having been presented to the Library, whereas it is only the first of the three volumes of that work which is as yet complete. Part vi., being the second part of the second volume, will be ready next week, and the succeeding parts will follow in due course. The error is not very important, but might mislead subscribers and others interested in the work.