262 Civil and Mechanical Engineering.

Then, when a float put out from the anchored boat approached the upper section line, the observer commenced counting the beats of his chronometer, and called his assistant by a few rattles of his key. The latter turntid his theodolite upon the flag, and followed it till a single touch of the key by his companion signalled its passing the upper line, when he clamped his theodolite and read the angle, the observer at the upper station recording the time of passing.

The float was signaled by the lower observer in the same manner when it passed his station.

This method apparently eliminated most of mentioned above, but still the results were not

(To be continued.)

the errors of location satisfactory.

Glass Ornamentation Made Easy.-Mr. Tilghman, whose ingenious process of cutting hard substances has attracted so much attention, informsus that sand falling from a height of about thirty feet upon glam will depolish its surface, and will, in fact, cut through the flash of colored glass. This affords an easy mode of experiment- ing in the ornamentation of glass, partially protected by paint or other means. The specimen of engraving to which we called atten- tion in September will shortly appear.

Horse Power of Steam Boilers,-We agaiu call attention to that portion of the report of the Committe on the Horse Power of Steam Boilers in which they request that any engineers who have made a trial of the heating surface required to evaporate a cubic foot of water per hour, on any well known type of boiler, would send the particulars of the result to the Secretary of the Franklin In- stitute.

The particulars desired in connection therewith are as follows : Description or sketch of boiler. Quantity of heating surface-

fire-box and flue. The setting of the boiler. Area of grate surface. Height of chimney. Natural or artificial draught. Kind of coal. Number of pounds consented per hour. Temperature of feed. Cubic feet of water evaporated per hour; and at what pressure of steam. Character of steam, wet or dry. Temperature of escaping gases. Duration of trial.