We returned yesterday with William to Philadelphia, and went to see the famous water-works, which supply the town with water from the Schuylkill. The water is thrown up by forcing-pumps to large reservoirs above; the surrounding grounds are very pretty, and the whole is made into a fashionable promenade, which commands a fine view of the city. We afterwards went to the penitentiary, which has a world-wide renown from its being the model of many which have been built in England and elsewhere. The solitary system is maintained, the prisoners never being allowed to see each other, nor could we see them. One poor man had been in confinement sixteen years out of twenty, to which he had been condemned. Any one remembering Dickens's account of this prison, must shudder at the recollection of it, and it was sad to feel oneself in the midst of a place of such sorrow. When here a few days ago, we had left our letters of introduction for Mr. Starr. He called to-day, and gave Papa some interesting information about the revivals. He takes great interest in the young _gamins_, whom I have described as "pedlering" in the railway cars, selling newspapers and cheap periodicals; they are a numerous class, and often sharp little fellows. Mr. Starr takes much pains in trying to improve their moral and religious characters. But I have no time at present for more. We returned to New York to-day, and are passing our last evening with William, who is to sail early to-morrow, and will be the bearer of this letter. LETTER VII. WILLIAM'S DEPARTURE.--GREENWOOD CEMETERY.--JOURNEY TO WASHINGTON.--ARRANGEMENTS FOR OUR JOURNEY TO THE FAR WEST.--TOPSY. Washington, 16th Oct. 1858. I closed my last letter to you on the 12th, and gave it to William to take to you. On the following day we bade him a sorrowful farewell, made all the more melancholy by the day being very rainy, which prevented our seeing him on board. We so very rarely see rain, that when it comes it is most depressing to our spirits, without any additional cause for lamentation; but it never lasts beyond a day, and is always succeeded by a renewal of most brilliant weather.