This section is from the book "Uncle Alberts Manual Of Practical Photography And Guide To The Reproductive Processes", by Powell Perry. Also available from Amazon: Uncle Alberts Manual Of Practical Photography And Guide To The Reproductive Processes.
"There have been so many humorous attempts at concealment of a camera that "to mention a ' hat' camera would, at first sight imply something similar. But "this is not so, because a full size quarter-plate is used, and covered as well. The "apparatus is simple enough notwithstanding, and can be fitted to any stiff form "of hat - the round billycock, or the chimney pot of the Metropolis. Even the "small hole necessary to permit the clear view of the lens can be so neatly cut, and "the part fitted so in as to attract no attention. The camera consists of a bellows "body, which lies flat in the ordinary way, but is extended by wires when required "for use. Special firm dark slides, of course, are necessary, and in addition there "is a focusing screen. The shutter is quickly got ready by placing, by a half-turn, "the release spring into its receptacle in the front of the hat. The camera alone "which is outlined in Fig. 1, weighs by itself 2 1/2 ozs. only. The method of use "is shown in Fig. 2.
Here we have a model (in scale, in glass) of the actual Felt-Hat Camera used by the author in his younger days to take the series of Instantaneous and Moving Object photographs used to illustrate my article on that subject (see page 30). The Operatic-Hat Camera is a variation of the above type and is used, in conjunction with the Umbrella Tripod, for general espionage and Night Club work.
Here we have a model (inaccurate, in wax), of the author with his Felt-Hat Camera deceptively poised in an attitude of old-world courtesy, whilst the index finger of the right hand hovers expectantly over the button. Further to conceal his intentions his left eye is seen to be focused on a point due west of where the camera is pointing - and presumably his right eye is focused on a point due east of same. It is doubtful whether the subject had the slightest idea she was being photographed.
"This is in the shape of a field-glass, one lens being used as a finder, and the other, "of course, for the exposures. When charged with plates it only weighs 19 ozs., "and is arranged for twelve exposures upon plates measuring 2 1/4 x 1 1/2 inches.
"Some idea of the arrangement and changing method may be gleaned from the "above (Fig. 2) illustration. It is very neat, effective in use, and the results "shown are good."