30 REPORT — 1844. 



tinued during the whole of the beautiful summer of 1 844, and many are now 

 in progress. It will be necessary to repeat these during another season ; and 

 I feel, therefore, under the circumstances of difficulty in which I am jjlaced 

 by the publication of very different results obtained on the other side of the 

 Atlantic, compelled to defer until the next meeting of the Association any- 

 thing like a regular report. I shall, however, place upon record a few of the 

 experiments, as they may serve to direct attention to an inquiry, in itself of 

 the greatest interest, and leading to the development of some of the most im- 

 portant problems connected with the dependence of organization and life on 

 the solar influences. 



It must be understood, unless it is distinctly stated to the contrary, that 

 the arrangements have been the same in principle, although on a much more 

 extended scale, as those which I have described in the report made to the 

 Association in 1842. 



I have used different absorptive media, and by a most careful prismatic 

 analysis of the rays by which they have been permeated, I have ascer- 

 tained with considerable correctness the condition of the rays which have 

 been in active operation. Not only have I examined tlie luminous spectrum 

 produced after the rays have undergone absorption, but I have ascertained 

 the relative quantity of the active chemical principle (Actinism) Avhich has 

 passed through the coloured glasses and fluids, by obtaining in every case 

 several spectra impressed upon photographic papers. 



I have found, that by using different thicknesses of glass, by superposing 

 glasses of different tints, and by varying the depth of colour in my solutions, 

 I have been enabled to procure with tolerable purity well-insulated rays. 



As in the former report I have spoken of the colours of the glasses and fluids 

 as bearing some relation to the unabsorbed rays, I shall continue to do so. 

 It will not be improper to state tliat the following arrangement may be re- 

 garded as fairly representing all the conditions of each experiment. When 

 I speak of a blue medium, it will indicate the presence of the most cliemi- 

 cally active rays. 



A RED MEDIUM the presence of the most calorific rays. 



A YELLOW MEDIUM the greatest amount of light with the least quantity of 

 heat and chemical power. 



A GREEN MEDIUM wiU indicate in most cases, light and chemical power 

 nearly balanced. 



On the 20th of March I sowed seeds of the sweet-scented pea in the open 

 ground, and in a box divided in partitions, so that each division was under 

 the influence of that light only which had permeated the media by which it 

 Avas covered. Under the influence of the blue and red media the seed ger- 

 minated six days before those sown in the open ground. The seed under the 

 yellow and green media germinated, and threw up their leaves at the same 

 time as those which had been placed under perfectly natural circumstances. 

 These pea plants were all of them allowed to grow until the 18th of April, 

 when tiiey were drawn from the soil ; their roots cut off, and the plants, 

 twelve from each compartment, carefully weighed. Their i-espective weights 

 were as follows : — 



Twelve plants grown under blue media 195^grs. 

 Twelve ])lants grown under red media 276 grs. 

 Twelve plants grown under green media 243^^ grs. 

 Tvvelve plants grown under yellow media 264 grs. 



It is important to notice, that all the plants which had grown under the 

 blue medium were of a fine fresh and healthy green colour. Those which had 



