I. Extract of a letter from Mr. William Arderon F. R. S. to Mr. Henry Baker, F. R. S. with the description of an improved hygroscope

Abstract

Dear sir , The great Mr. Boyle has taken much Pains to bring the Hygrometer to Perfection; and Mr. Roger Pickering , one of your ingenious Members, has * lately made an Improvement to it: But, as the Instrument I use differs from them both, I shall beg Leave to describe it to you.