Only two more numbers to be issued, and the curtain drops upon Volnme XIII. of the SCIENTIFIC AHUICAN. All subscriptiona that began with this volume will end with No. 52, and in accordance with our usual custom, the paper will be stopped unless they are renewed. Friends, send in your subscriptions with as little delay as possible. Get some of your neighbors to join with you, and thus avail yourselves of our liberal clubbing rates. EXHIBITORS OF MACHINES are invited to notice the advertisement of the Mechanic's Institute of Chicago on mother pge.