A TYPICAL STAR CLUSTER-CENTAURI
THE GLASS DISK
THE OPTICIAN'S TOOL
THE OPTICIAN'S TOOL
GRINDING A LARGE LENS
IMAGE OF CANDLE-FLAME IN OBJECT-GLASS
TESTING ADJUSTMENT OF OBJECT-GLASS
A VERY PRIMITIVE MOUNTING FOR A TELESCOPE
THE HUYGHENIAN EYE-PIECE
SECTION OF THE PRIMITIVE MOUNTING