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basically, the whole thing was wrong. No incident in a plant's career could be considered as of any scientific value if that plant were placed, even temporarily, under the horrible conditions then available. Daylight was decided to be essential, but its introduction obviously meant a complete revolution of the existing apparatus and methods of procedure. In designing the outfit I was still obsessed with the quasi-perpetual motion mania, although obviously when subjects are sufficiently interesting to be inspected several times a day a machine working for weeks unaided was perfectly unnecessary.
An attic was requisitioned, and its window fitted with a series of light shutters which could be opened or shut by pulling or releasing a string. A table near to it carried the camera, motor, lighting apparatus, etc., and over the table hung a cuckoo clock. At the point of the table where the weight of the clock touched, an electric burglar alarm contact was placed. A toy electric motor attached to a train of clock wheels slowly and pretty powerfully turned a spindle which by more or less orthodox devices was connected with the single turn of the camera, the shutters of the window, the tap of an incandescent gas jet, and the chain of the cuckoo clock. A 4 volt accumulator, my first acquaintance with electricity, was used as motive power.
Normally, the gas was on a bye-pass, the shutters open, the plant moderately illuminated, helped out with mirrors opposed to the window, and the clock ticking. As soon as the descending weight pressed on the contact the motor started up, slammed the shutters, opened up the light, took a picture, turned out the light, reopened the shutters and finally by means of a lever pulled the chain of the clock and lifted the weight. Arrangements were made for considerably varying the amount of pull on the chain, thus altering the interval between the pictures.
With gas as the source of illumination the inverted burner was naturally selected both on account of its efficiency and desirable shape. It was soon found, however, that it possesses a serious fault, namely that a slight variation of pressure in the gas supply caused very considerable alteration in the light emitted. The upright burner was substituted and found far less sensitive to alteration of pressure. The upright mantle is, at first sight, not at all well adapted to the illumination of a horizontal picture. Used in conjunction with the usual type of condensers the illuminated field available is merely that of a section of one third or less of the total area of the mantle. This, however, is actually an advantage, for in the case of pressure variation the central section of the mantle fluctuates distinctly less than its extremities. For photographing plants, this central section of the mantle gives, with suitable condensers and reflectors, all the light that is required. In cases where it is insufficient, as, for example, in low power photo-micrography, useful results may be obtained by placing the light very low down