Back Numbers and Volumes—In reply to many interrogatories as to what back numbers and volumes of the Scientific American can be furnished, we make the following statement —Of Volumee 1, 2 and 3—none. Of Volume 4, about 20 Nos., price 60 eta. Of Volume 5, all but four numbers, price, in sheets, $1. Of Volume 6, all; price in sheets, $2; bound,$2,76 Of Vol. 7, all; price in sheets, $2; bound, $2,75. Of Vol. 8, none.