My father has just returned from Dr. Darwin's, where he has been nearly three weeks: they were extremely kind, and pressed him very much to take a house in or near Derby for the summer. He has been, as Dr. Darwin expressed it, "breathing the breath of life into the brazen lungs of a clock" which he had made at Edgeworthstown as a present for him. He saw the first part of Dr. Darwin's _Botanic Garden_; £900 was what his bookseller gave him for the whole! On his return from Derby, my father spent a day with Mr. Keir, the great chemist, at Birmingham: he was speaking to him of the late discovery of fulminating silver, with which I suppose your ladyship is well acquainted, though it be new to Henry and me. A lady and gentleman went into a laboratory where a few grains of fulminating silver were lying in a mortar: the gentleman, as he was talking, happened to stir it with the end of his cane, which was tipped with iron,--the fulminating silver exploded instantly, and blew the lady, the gentleman, and the whole laboratory to pieces! Take care how you go into laboratories with gentlemen, unless they are like Sir Plume skilled in the "nice conduct" of their canes. Have you seen any of the things that have been lately published about the negroes? We have just read a very small pamphlet of about ten pages, merely an account of the facts stated to the House of Commons. Twenty-five thousand people in England have absolutely left off eating West India sugar, from the hope that when there is no longer any demand for sugar the slaves will not be so cruelly treated. Children in several schools have given up sweet things, which is surely very benevolent; though whether it will at all conduce to the end proposed is perhaps wholly uncertain, and in the meantime we go on eating apple pies sweetened with sugar instead of with honey. At Mr. Keir's, however, my father avers that he ate excellent custards sweetened with honey. Will it not be rather hard upon the poor bees in the end?