Chapter II: TECHNOLOGY.--Critical Methods of Detecting Errors in Plane

Surfaces.--By JOHN A. BRASHEAR.--11 figures.

Photometric Standards.--9 figures.

Bleaching or Dyeing Yarns and Goods in Vacuo.--1 figure.

On the Moulding of Porcelain.--By CHAS. LAUTH.--Moulding by
pressure of the air.--Moulding by vacuum.--Drying the moulded
pieces.--2 figures.

Photo-Tricycle Apparatus.--1 figure.

A Photo Printing Light.--1 figure.

A New Actinometer.

Astronomical Photography.

Electricity as a Preventive of Scale in Boilers.