5ff REPORT — 1855. 



deposited where no living beings existed ; for although the absence of organic remains 

 in them might be accounted for by metamorphic action, the heat which obliterated 

 the latter would exert no influence upon the phosphoric acid which all animals and 

 vegetables contain, and which therefore would still remain in a rock made up in part 

 of their exuviae, even if it had undei-gone fusion. 



Dr. Daubeny suggested that this method of investigation might throw some light 

 upon the much-disputed question, whether any rocks are known which were ante- 

 cedent to the commencement of organic life ; and also, in a practical point of view, 

 might be useful by showing, whether manuring with phosphate of lime was likely to 

 be serviceable in increasing their agricultural value. 



The second subject adverted to in this communication related to the reputed exist- 

 ence of phosphoric acid in certain rocks of Connemara in Ireland, which Sir Roderick 

 Murchison liad referred to the Silurian epoch. 



These limestones, although totally destitute of organic remains, and possessing all 

 the characters of primitive limestone, being crystalline and interstratified with quartz 

 rock and mica slate, often contain, according to a recent analysis, a large per-centage 

 of phosphoric acid ; and this statement, Dr. Daubeny, from a hasty examination which 

 he had made of them upon the spot, was disposed to credit, so far at least as relates to 

 the presence of traces of this ingredient in the limestones referred to*. 



Should this fact be substantiated by further investigations, it will not only confirm 

 Sir R. Murchison 's previous opinion as to the age of these limestones, but will also 

 show that they are likely to be of value as manures, by reason of the phosphoric 

 acid which they contain. 



On tlie Action of Light on the Germination of Seeds, 

 By Professor Daubent, 3LD., F.R.S. 



An opinion has gone abroad, and has found a place in several standard treatises f, 

 that as the luminous rays favour the development of the growing plant, so the chemical 

 rays promote the germination of the seed. 



The authority upon which this statement rests, seems to be that of some experiments 

 instituted by Professor Robert Hunt, who, whilst employed in investigating the che- 

 mical action of light upon inorganic bodies, and its application to photography, turned 

 his attention likewise to the influence of the same agent upon plants. 



One circumstance alone, however, might raise a doubt as to any direct effect having, 

 in the instances reported, been produced by the several solar rays, namely that, so far 

 as can be collected from the statement given, all the seeds tried by Mr. Hunt were 

 buried in the ground to the usual depth. Now I found that a depth of two inches of 

 common garden soil was quite sufficient to intercept the rays of light, so as to prevent 

 the slightest chemical action being exerted upon highly sensitive paper placed be- 

 neath it. 



The improbabilit}', therefore, of a ray of light acting through such a medium in- 

 duced me to institute a set of experiments, in which the seeds were placed on the 

 sui-face of moist earth exposed to the action of particular portions only of the solar 

 spectrum. 



Although the results obtained are rather of a negative than of a positive descrip- 

 tion, and have likewise been in some measure superseded by the researches already 

 published by Dr. Gladstone, yet as the experiments have been repealed during the 

 last summer, and lead uniformly to similar results, they are communicated, as justi- 

 fying the conclusion to which I had arrived, that no positive influence of a direct 

 kind in promoting germination can be traced to the chemical rays of light, when 

 compared with other portions of the sunbeam. 



Six sorts of seeds were in general employed in these experiments, and the number 

 of radicles and plumules of the several kinds which had protruded each day were 

 duly registered. 



The media employed for isolating certain rays, or at least particular portions 



* These limestones have been since examined more carefully by Dr. Daubeny, and the 

 quantity of phosphoric acid present in them found to be much smaller than that reported 

 in the analysis referred to. See Proceedings of the Ashmolean Society for Oct. 29, 1855. 



t See in particular Mrs. Somerville's work on Physical Geography. 



