158 PROCEEDINGS OP THE MICROSCOPICAL SOCIETY OF DUBLIN. 



the scarlet biniodide of mercury is subjected to the influence of heat 

 and sublimed, and the passage of the yellow resulting crystals back to 

 the original scarlet from various causes, details a series of most in- 

 teresting microscopic observations on this subject from which he con- 

 cludes that the resumption of the scarlet colour is owing to a series of 

 changes taking place, which separate, to a certain extent, the laminae 

 of the crystals from each other, that this is determined more rapidly by 

 mechanical disturbance of the surfaces from various enumerated causes, 

 and that the yellow colour can be again produced, without materially 

 altering the form, by carefully fusing together the separated plates of 

 the altered crystals by a rapid application of heat. The author also 

 states that when the heat is gradually applied a mixture of red and 

 yellow crystals are produced, each having its proper and distinct form, 

 but if suddenly submitted to a higher temperature, nothing but the 

 yellow crystals result, proving that this compound is dimorphous, and 

 has two distinct vapours at varying temperatures. 



Mr. W. then goes on to investigate the changes of colour which 

 take place when the biniodide is formed by precipitation from solutions, 

 and finds that the yellow powder which at first appears, is in the form 

 of the sublimed yellow crystals, and that these are after a short time 

 redissolved slowly producing the formation of red crystals of the same 

 shape as those obtained by the gentle application of heat to the dry 

 compound ; a phenomenon new in the subject of crystalization, and 

 highly interesting. This paper was illustrated by drawings of the crys- 

 tals taken from the microscope by the camera lucida. The powers em- 

 ployed were 250 and 620 diameters. 



PROCEEDINGS OP THE MICROSCOPICAL SOCIETY OP DUBLIN. 



March 3rd, 1842. J. F. Bergin, Esq., President, in the Chair. 



THE Secretary having read the proceedings of the last meeting, 



Mr. Allman read a very interesting paper on the reproduction of 

 Entozoa. 



Mr. Grubb exhibited a block of pine wood, which had formed part 

 of a pile taken up from the bed of the Shannon, near Tarbert, where it 

 had been lying for five years ; it was found penetrated by numerous 

 tabular canals of Teredo navalis, and was rendered completely cellular 

 by Lemnoria. 



Mr Callwell presented some specimens of minute Algae, Calathamniwn 

 Corymbosa, &c. 



Dr. Hill exhibited several specimens of minute arterial injections of 

 the human kidneys. 



April I4th, 1842. T. F. Bergin, Esq., President, in the Chair. 



THE Minutes of last meeting having been read 



Mr. Callwell mentioned that he had obtained specimens of minute 

 Algae which had grown on a solution of Iodide of Potassium. 



