70 Miscellaneous. 



vegetation, but, further, we can modify its course, delay the action 

 of certain functions, or enlarge the development and the modifica- 

 tion of certain organs. The author further remarks, that if its use 

 be ill-directed, it may cause accidents. Those vtrhich have occurred 

 in the course of his experiments appear to him to throw an unex- 

 pected light upon the mechanism of the nutrition of plants. They 

 have at least taught him at the expense of what care ammonia may 

 become an auxiliary of vegetation. These experiments, which were 

 made under the same conditions as those upon the absorption of 

 azote, are then described, and their numerical results given. 



To the conclusions already stated, the author adds that there are 

 periods to be selected for the employment of ammonia, during which 

 this gas produces different effects. If we commence its use when 

 several months intervene before the flowering season of the plants, 

 it produces no disturbance ; they follow the ordinary course of their 

 vegetation. If its use be commenced at the time of flowering, this 

 function is stopped or delayed. The plant covers itself with leaves, 

 and if the flowering takes place all the flowers are barren. — Proc. 

 Roy. Soc. May 26, 1833. 



On the Priority of the Discovery of the Mode of Action of the 

 Pholades in the Perforation of Stones. By M. Vrolik. 



The question of the perforation of rocks by Pholades, which has 

 been brought before the Academy of Sciences, has given rise to a 

 claim of priority put forwaa'd by Mr. Robertson, and since contested 

 by M. Caillaud. 



The Academy will not be displeased to learn that Professor Vrolik 

 of Amsterdam has just shown that the fact of mechanical perfora- 

 tion by the valves, and as the result of the simple movement of the 

 Pholades, without the assistance of any acid, was described more than 

 seventy years ago by Leendert Bomme, a Director of the Commercial 

 Company of Middelbourg. His memoir, in which he enters into 

 many details respecting the ceconomy of these animals, which in 

 1759 and 1760 threatened the destruction of the dykes of the island 

 of "Walcheren, was published in the Transactions of the Scientific 

 Society of Flessingen. — Comptes Rendus, May 2, 1853. 



On Sun Columns observed at Sandwick Manse, Orkney. 

 By the Rev. C. Clouston. 



May 18th. About 8 p.m. observed a mock sun having prismatic 

 colours, on the N. side of the sun, with rays on the off side converging 

 to a point. In about 15 minutes another of the same description, but 

 fainter, appeared on the S. side of the sun, and a faint halo appeared 

 over the sun, as if joining there. At sunset there was a faint sun 

 pillar. 



21st. At sunset another sun pillar seen. 



23rd. A sun pillar seen tonight at 8 p.m., about 45 minutes before 

 sunset, at first being a pale whitish beam, shooting up through the 



