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 Volumes 1, 2 and 3—none Of Volume 4, about 20 Nos., price 50 cte. OfVolume 5, all but eight numbers, price, in tiheeta, 81. OfVolume 6, all; price in sheets, $2; bound, $2,75 Of Vol. 7, all; price in sheets, $2; bound, $2,75. Of Vol. 8, none.