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The results hitherto obtained indicate, in general, a very low order of efficiency in storage of energy. The methods employed have been defective from absence of means of exact measurement of the incident energy, from the indeterminate loss of the energy received and from the difficulty in the exact determination of the energy stored. The efficiency is found from the ratio of the energy stored Es, to the energy absorbed Ea.

I have been successful in obviating the various difficulties in the accurate determination of the energy absorbed, and of the energy stored. The energy absorbed is found by two different methods, the Calorimetric and the Radiometric, these two independent determinations following each other in quick succession. While the energy absorbed is being determined, simultaneous measurement is made of the energy stored by the production of carbohydrate. This is calculated from the volume of oxygen evolved.

The efficiency of the photosynthetic organ is found to be much higher than had been usually supposed, being half that of an ordinary steam engine. In vigorous Hydrilla plant it is as high as 7.4 per cent.

The automatic method of record that has been described, can also be utilised in physico-chemical investigations, such as the determination of the rate of evolution of a gas under controlled conditions of temperature, of concentration, of intensity of light, of catalytic agents and others, either separately or in combination. It is obvious how it can be applied in various