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through the solution in the close apparatus, in its way to the neg» 

 tive side. 



I must here remark; that the electric current, immediately on it* 

 first application, was observed to decompose the solution with 

 such energy, that I deemed it advisable to suspend the operation 

 until the activity of the battery should be somewhat modified, and 

 it was not until the evening of the 6th of May that I could date 

 the commencement of my experiment. 



A circumstantial record of all important changes connected 

 with this experiment has been preserved, up to the present day, 

 embracing a period of three years and three months, but I cannot 

 conclude that any extracts from my memoranda would enhance 

 the interest of the present notice. I shall therefore prefer a brief 

 summary of the results ; first premising that two excellent con- 

 stant batteries have been successively worn out in the undertaking, 

 and that the requisite changes were made without interruption to 

 the electric current, which is now transmitted by a water-battery 

 of twenty pairs, working with the characteristic uniformity of this 

 excellent species of voltaic contrivance. I would further remark 

 that, from the commencement of the experiment, the battery and 

 the respective vessels containing the solutions have been strictly 

 excluded from the light, by means of a screen constructed for the 

 occasion, and the entire proceeding has been confined to a retired 

 room kept constantly locked, no one having access unless accom- 

 panied by myself. My general habit has been to visit the arrange- 

 ment once in two days, for the purpose of noting the progress, 

 supplying the battery with crystals of sulphate of copper, making 

 good the loss of fluids caused by the evaporation, &c. 



1. October 19th, 1842— one hundred and sixty-six days from the 

 commencement of the experiment — the first acari seen in connec- 

 tion therewith, six in number and nearly full-grown, were dis- 

 covered on the outside of the open glass vessel. On removing 

 two pieces of card which had been laid over the mouth of this ves- 

 sel, several fine "specimens were found inhabiting the under sur- 

 faces, and others completely developed and in active motion here 

 and there within the glass. * 



October 20th. — Making my visit at an hour when a more favora- 

 ble light entered the room, swarms of acari were found on the 

 cards about the glass tumbler, both within and without, and also 

 on the platform of the apparatus. At this identical hour Dr. J. 

 Black favored me with a call, inspected the arrangements, and 

 received six living specimens of the acarus produced from solution 

 in the open vessel. No trace of insect life could at this time be 

 discovered in the close vessel with an oxygen atmosphere. The 

 solution in the open vessel had undergone very slight change of 

 color, but exhibited a multitude of minute and beautifully colored 

 crystals with a prevailing tinge of crimson. The solution beneath 

 the oxygen atmosphere, about ten days after the voltaic current 

 began to traverse it, had assumed a reddish-brown appearance, 

 which gradually darkened in color until scarcely any light could 

 be transmitted through it, or the ascent of gas from either of the 

 electrodes perceived. 



2. Myriad? of acari continued to be developed from the solution 

 in the open vessel until the 20'h August, 1843, when it was found 

 expedient to determine this division of the experiment, and confine 

 the operation of the electric current solely to the close arrange 



