Gurney's Sensitive.--This is another preparation of bromine, and gives a fine tone. To two parts of water add one of the sensitive, and put just sufficient in the box to cover the bottom, or enable you to coat in from eight to ten seconds. Coat over dry iodine to a dark yellow, and over the quick till you see a good change, then back over the dry iodine from two to three seconds. Bromide of Lime, or Dry Sensitive.--This is a compound but recently introduced, and is becoming somewhat of it favorite, owing principally to the slight trouble it gives in its preparation, and the tone it imparts to the picture. To prepare it, fill your jar about half or quarter full of dry slacked lime, then drop into it bromine, till it becomes a bright orange red. The plate is generally coated over this compound, after the iodine coating to yellow, to a violet, or plum color; but it will work well under any circumstances, the color being of little consequence, if coated from thirty to ninety seconds, according to its strength. Mead's Accelerator.--I merely mention this as being in the market, not knowing any thing in regard to its merits. The directions given for its use are as follows: Mix one-third of a bottle with a wine glass full of water, coat the plate over dry iodine to a dark gold color, then over the accelerator to a violet, then back over dry iodine, or chloride of iodine, from three to five seconds. Chloride of Bromine.--M. Bissou, a French experimentalist, has found that bromine associated with chlorine, prepared in a similar manner to chloride of iodine, already described, a solution of bromine being substituted for the iodine, is a very sensitive solution; by means of it daguerreotype proofs are obtained in half a second, and, thus very fugitive subjects are represented, making it the very best compound for taking children. So quick is its operation, that even persons or animals may be taken in the act of walking. Hungarian Liquid.--This, I believe, has never been used here, or imported into this country, and the composition of it is not generally known, even in Europe, where it has taken precedence of all others. It acts quickly and with considerable certainty. It is used by diluting it with from ten to fifteen times its bulk of water, putting a sufficient quantity into the jar to cover the bottom. The plate being previously iodized to a light yellow, is submitted to this mixture till it assumes a light rose tint. Bromine and Fluoric Acid, in combination, are used by some Daguerrean artists as a sensitive, but any of the above compounds are better; besides this, the fluoric acid is a dangerous poison, and the quick made from it will not repay the risk to the health in using it.