Chapter II: TECHNOLOGY.--A Method of Measuring the Absolute Sensitiveness

of Photographic Dry Plates.--By Wm. H. PICKERING.--From the
proceedings of the Academy of Arts and Sciences.

Soldering and Repairing Platinum Vessels in the
Laboratory.--By J.W. PRATT.

The Helicoidal or Wire Stone Saw invented by M.P. GAY.--With
engraving of quarry showing application of saw, and 5 figures.

Portable Prospecting Drill and Automatic Safety Gear shown at
the Inventions Exhibition.--With 2 engravings.