MESSRS. EDITORS In No. 7, page 53, of the Scientific American, you appeal to your Pennsylvania friends, by whom you doubtless mean Mr. Birkinbine and myself, to answer a communication you received trom J. D. Rice, of Philadelphia ; I have waited until this time to see what reply Mr. Birkinbine would make to this appeal, but as he has made none, I feel compelled, in self-defence to state how far this communication has any reference to me. As to the ram at Naples, N. Y., I never had any thing to do with it, and the first intimation I ever had of its not succeeding, was through the communication of Mr. Rice. All that I had to do with the ram at Girard College, was to calculate and make a draught of the curve of quickest descent for the driving pipe ; this I did at the request of Mr. Henry Tatham, who took a deep interest in the concern, and recommended the works to be erected, and through whom I sent the calculations and draught to Mr. Birkinbine, who, I infer from letters I received from him afterwards, laid it out accordingly. I understand, by those who ought to know, that this ram was discontinued only on account of the feed-water becoming too small for the increased demand, and not to anything depending on either Mr. Birkinbine or myself. If I have stated, above, anything incorrect, Mr. Birkinbine can correct me. JOSEPH C. STRODE.