TRANSCRIBER'S NOTES Italic text is denoted by _underscores_ and bold text by =equal signs=. The picture of a pointing finger, known in typography as an index, a manicule, or a fist, has been rendered in this text version as "=>". Subscripts have been rendered using braces, so that the formula for sulphuric acid is shown as "H{2}SO{4}", and the formula for water, if it had appeared, would have been shown as "H{2}O". * * * * * [Illustration: SCIENTIFIC AMERICAN] A WEEKLY JOURNAL OF PRACTICAL INFORMATION, ART, SCIENCE, MECHANICS, CHEMISTRY, AND MANUFACTURES. Vol. XXXIX.--No. 6 NEW YORK, AUGUST 10, 1878 $3.20 per Annum. [NEW SERIES.] [POSTAGE PREPAID.] THE PARIS EXHIBITION.--A SKETCH IN THE PARK. Our engraving, which represents a portion of the park at the Paris Exhibition grounds, needs little mention beyond that it is one of those delightful retreats so refreshing to the weary visitor, who, tired out with tramping about the buildings and grounds, is only too pleased to refresh his eyes with some of that exquisite miniature water scenery which is scattered about the grounds. We take our illustration from the London _Graphic_. * * * * * =Improvements in Silk Worm Breeding.= _Galignani_ states that a very curious discovery has just been made, which, if found as practicable in application as it seems to promise, may create a very considerable change in the production of silk. It is nothing more nor less than the possibility of obtaining two yields in the year of the raw material instead of one, as at present. The moth lays its eggs in May or June, and these do not hatch before the spring of the following year. But sometimes they are observed to hatch spontaneously ten or twelve days after they are laid. It was such a circumstance as this coming to the attention of M. Ducloux, Professor of the Faculty of Sciences at Lyons, that led him to undertake a series of experiments on the subject, by means of which he has found that this premature hatching can be produced at will. The means for effecting the object are very simple--rubbing the eggs with a hair brush, subjecting them to the action of electricity, or more surely still by dipping them for half a minute in concentrated sulphuric acid. M. Bollé, who has also turned his attention to the same subject, states that the same effect is produced by hydrochloric, nitric, or even acetic and tartaric acid. Finally, a submersion of a few seconds in water heated to 50° Cent. (122° Fah.) is equally efficacious. However, M. Ducloux states that the operation must be performed while the eggs are quite young, the second or third day at the outside. When this new hatching is accomplished the mulberry tree is in its full vigor, and the weather so favorable that the rearing of the worm is liable to much less risk than during the