This number completes the first six months of Vol. 8, Scientific American, and we return our sincere thanks to our friends for their liberal and hearty patronage. Our circulation has greatly increased, and had we commenced the present volume with printing five thousand more copies than the number we have issued, we would have found subscribers for them all. We hope that those of our subscribers whose half-yearly term now expires, and who have not renewed their subscriptions, will do so at the earliest opportunity, in order that they may have all their numbers complete. Every article is finished in this number, and the next half of the volume will be commenced with new articles, so that new subscribers will have an excellent opportunity of beginning with a number, the first of 26 that will form a half volume complete in itself. As the Crystal Palace will be open this summer, our pages will be embellished with many beautiful engravings of interesting machinery displayed there, and our columns will be furnished with information which no mechanic, artisan, or man of science can well do without, and be posted up with the progress of the age. To secure future numbers, we urge upon our readers to send in their subscriptions early, as it has been a subject of regret to us that we had to say to so many, all our back numbers are gone/ As our circulation has increased we have improved the Scientific American, and this onward course and policy we shall always pursue. W shall print an extra quantity of our next number in order to meet new demands, and with honesty and truth for our mottoes ; a desire to be severely correct in the information we obtain ; and with energy, means, and enterprize, to obtain the most reliable and earliest intormation about inventions and scientific matters, we trust that before another year passes away we will be able to say, the Scientific American has 30,000 subscribers. We ought to have this number now, considering the amount of our population ; and with the influence and kind interest of our readers among their friends, we hope to obtain it. If every subscriber would get a new subscriber the result would be accomplished. We believe such a result (while we confess it would greatly benefit us,) would also benefit our people, as the information we present is really useful and elevating, not only instructive for a day but for all generations.