376 CALORIFIC INFLUENCE. 



These experiments, simple as they are, prove to us 

 the importance of light : the luminous principle of the 

 sunbeam is exciting the vital powers of the plant to 

 decompose carbonic acid and form wood; and the 

 calorific agent, possibly under those modifications which 

 have already been noticed as belonging to the para- 

 thermic rays, is essential to the production of flower and 

 fruit. 



Observations, which have been extended over many 

 years, prove that with the seasons these solar powers are, 



principle is active, as the value conies to be depreciated in the 

 ratio it is found to he dormant. For instance, if we sow 100 

 seeds of any sort, and the whole| germinate, the seed will be the 

 highest current value-; but if only 90 germinate, its value is 10 

 per cent, less; if 80, then its value falls 20 per cent. 



I merely give this detail to show the practical value of this- 

 test, and the influence it exerts on the fluctuation of prices. 



Our usual plan formerly was to sow the seeds to be tested in a 

 hot-bed or frame, and then watch the progress and note the results. 

 It was usually from eight to fourteen days before we were in a 

 condition to decide on the commercial value of the seed under 

 triaL 



My attention was, however,, directed to your excellent work, 

 " On the Physical Phenomena of Nature," about five years ago,, 

 and I resolved to put your theory to a practical test. I accordingly 

 had a case made, the sides of which were formed of glass coloured 

 blue or indigo, which case I attached to a small gas stove for 

 engendering heat; in the case shelves were fixed in the inside, on 

 which were placed small pots wherein the seeds to ba tested were- 

 sown., 



The results were all that could be looked for: the seeds freely 

 germinated in from two to five days only, instead of from, eight to> 

 fourteen days as before. 



I have not earned our experiments beyond the germination of 

 seeds, so that I cannot afford practical information as to the effect 

 of other rays on the after culture of plants. 



I have, however, made some trials with the yellow ray in pre- 

 venting the germination of seeds, which have been successful ; 

 and I have always found the violet ray prejudicial to the growth 

 of the plant after germination. I remain, my dear Sir, 

 Very faithfully yours, 



CHARLES LAWSON* 



