irritation and impatience--when we were stupid or inattentive, neither of which she could stand. With her clear mind she darted at the solution, sometimes forgetting that we had to toil after her laboriously step by step. I well remember her slender white hand pointing impatiently to the book or slate--"Don't you see it? there is no difficulty in it, it is quite clear." Things were so clear to her! I must here add some other recollections by my mother of this very interesting portion of her life.] * * * * * I was a considerable time employed in writing this book, but I by no means gave up society, which would neither have suited Somerville nor me. We dined out, went to evening parties, and occasionally to the theatre. As soon as my work was finished I sent the manuscript to Lord Brougham, requesting that it might be thoroughly examined, criticised and destroyed according to promise if a failure. I was very nervous while it was under examination, and was equally surprised and gratified that Sir John Herschel, our greatest astronomer, and perfectly versed in the calculus, should have found so few errors. The letter he wrote on this occasion made me so happy and proud that I have preserved it. LETTER FROM SIR JOHN HERSCHEL TO MRS. SOMERVILLE. DEAR MRS. SOMERVILLE, I have read your manuscript with the greatest pleasure, and will not hesitate to add, (because I am sure you will believe it sincere,) with the highest admiration. Go on thus, and you will leave a memorial of no common kind to posterity; and, what you will value far more than fame, you will have accomplished a most useful work. What a pity that La Place has not lived to see this illustration of his great work! You will only, I fear, give too strong a stimulus to the study of abstract science by this performance. I have marked as somewhat obscure a part of the illustration of the principle of virtual velocities.... Will you look at this point again? I have made a trifling remark in page 6, but it is a mere matter of metaphysical nicety, and perhaps hardly worth pencilling your beautiful manuscript for. Ever yours most truly, J. HERSCHEL.