134 Miscellaneous. 



cloud formed by the living mass, that it completely obscured the sun 

 from people on board our continental steamers on their passage for 

 many hundreds of yards, while the insects strewed the decks in all 

 directions. The flight reached England about twelve o'clock at noon 

 and dispersed themselves inland and along shore, darkening the air 

 as they went. During the sea passage of the butterflies the weathei 

 was calm and sunny, with scarce a puff of wind stirring, but an hour 

 or so after they reached terra firma it came on to blow great guns 

 from the S.W., the direction whence the insects came." — Canterbury 

 Journal. 



If the time occupied in the passage over could be ascertained it 

 would also be interesting — at all events the hour at which they were 

 observed by the people on board the steamer and the distance from 

 land could be ascertained, and that would go some way towards the 

 rate at which they travelled, the period of their arrival being stated. 



I am, dear Sir, yours very truly, 



Henry Denny, A.L.S. 



Do Plants placed in a Solution containing several Substances, absorb 

 certain Substances in preference to others ? By M. Bouchard at. 



Theodore de Saussure, who made so many beautiful experiments 

 on vegetation, has answered the question which I have here pro- 

 posed in the affirmative ; but the results which he obtained do not 

 appear to me sufficiently free from all chances of error to render it 

 unnecessary to return to this subject. The way in which the expe- 

 riments of Theodore de Saussure were made may be stated in a few 

 words. He dissolved in 793 cubic centimetres of water two or three 

 different salts, each weighing 637 milligrammes ; he analysed the 

 residue of the solution when it was reduced one-half by absorption 

 by the roots of the plants. The quantity of salts contained in the 

 residue, minus that which the liquid contained before the introduction 

 of the plants, indicated the quantity of salts absorbed. Theodore de 

 Saussure saw that with several salts this quantity was very unequal ; 

 thus, to cite only one example, in a mixed solution of nitrate of lime 

 and muriate of ammonia, a Polygonum absorbed two of nitrate of lime 

 and fifteen of muriate of ammonia. 



The differences were particularly great with the soluble salts of 

 lime ; their absorption appears infinitely less easy than that of several 

 other salts ; but the following experiment throws much doubt on 

 the conclusion to be drawn from the facts cited by Theodore de 

 Saussure. 



In a solution in distilled water containing one gramme of sulphate 

 of soda and one gramme of chloride of sodium to the litre, I planted 

 a Polygonum persicaria, and when half the solution was absorbed, I 

 examined the residue, and found in it, besides the oxalate of ammo- 

 nia, a notable quantity of lime, which did not exist in it previously, 

 and which had been furnished by the vegetable. 



This then is one capital cause of etror which escaped Theodore de 

 Saussure. 



When a vegetable is immersed in an aqueous solution, there ia 



