Smithsonian miscellaneous collections . eal filter, has certain advantages for an experiment of thisnature. By merely changing the temperature of the filters it waspossible to cover the entire spectral region of photosynthesis by usingtwo filters with different proportions of carbon disulphide and benzene.Tn the first experiment with these filters, four filters 6 inches in NO. 21 CO2 ASSIMILATION AND WAVE LENGTH HOOVER 3 diameter and 2 inches thick were used in order to illuminate the plantson four sides. The temperature of the filters was controlled by placingthem in thermostated water baths.

Smithsonian miscellaneous collections . eal filter, has certain advantages for an experiment of thisnature. By merely changing the temperature of the filters it waspossible to cover the entire spectral region of photosynthesis by usingtwo filters with different proportions of carbon disulphide and benzene.Tn the first experiment with these filters, four filters 6 inches in NO. 21 CO2 ASSIMILATION AND WAVE LENGTH HOOVER 3 diameter and 2 inches thick were used in order to illuminate the plantson four sides. The temperature of the filters was controlled by placingthem in thermostated water baths. Stock Photo
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The Reading Room / Alamy Stock Photo

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2AJHKN8

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1958 x 1277 px | 33.2 x 21.6 cm | 13.1 x 8.5 inches | 150dpi

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Smithsonian miscellaneous collections . eal filter, has certain advantages for an experiment of thisnature. By merely changing the temperature of the filters it waspossible to cover the entire spectral region of photosynthesis by usingtwo filters with different proportions of carbon disulphide and benzene.Tn the first experiment with these filters, four filters 6 inches in NO. 21 CO2 ASSIMILATION AND WAVE LENGTH HOOVER 3 diameter and 2 inches thick were used in order to illuminate the plantson four sides. The temperature of the filters was controlled by placingthem in thermostated water baths. A very simple optical system wasused in this case. A looo-watt Mazda lamp was placed near the focusof a concave mirror in order to obtain a magnified image of thesource at the plant. The light passed twice through the filter beforereaching the plant. Figure i represents the energy distribution ob-tained with these filters under the condition of the experiment. Thedistribution of energy in the bands was not entirely satisfactory, owing. Fig. I.—Energy transmission curves for 6-inch Christiansen filters. to imperfections in the concave mirrors and to the fact that the filterswere too thick to obtain good temperature control. In the second experiment with the Christiansen filters sunlightwas used as the source of radiation. Sunlight was obtained for theexperiment by using a large coelostat located on the south side of theSmithsonian building. The moving mirror of the coelostat was 30inches in diameter. Light reflected from this mirror was reflected bya second mirror to a third mirror located at one end of a long room.This mirror was about 60 feet from the plants. This combination ofmirrors illuminated an area at the plant chamber about 15 inches indiameter. A Christiansen filter 12 x 14 inches and i inch thick wasmade in order to use most of the energy in this beam. The filter wasplaced 50 feet from the plant chamber. The distribution of energy in SMITHSONIAN MISCELLANEOUS COLL

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