SIR,--I beg leave to tender my sincerest thanks for your kind notice in the last _Gazette_ of my recent discoveries on the treatment of diseases of the eye, &c. Allow me to intrude for once in your crowded columns, by referring to what you accidentally omitted--viz. the manner of applying the _bisulphuret of carbon_, and also to add a few reasons illustrative of the fact which you have quoted from me, that its action depends on its union with the oxygen. The plan I adopt is this:--I put a drachm of the bisulphuret of carbon into a two-ounce bottle; the medicine is so volatile that the heat of the hand causes the vapour rapidly to rise, and come into contact with the skin. The action is more decided if the skin is previously moistened with water; as the water not only prevents the escape of the vapour between the glass and the skin, but also excludes the external air, a point of the very highest importance. In my paper, which appeared in the _Lancet_, of October 29th, I stated, that "when it had been applied about one minute, the patient felt the part very cold, but immediately after a gradual heat, accompanied with great prickling; the heat increasing the longer the medicine was kept in contact with the part, until it could no longer be endured. On removing the glass the part was red, to an extent two or three times greater than the part enclosed. These applications occasion no injury whatever to the skin." Showing that the action of the bisulphuret of carbon depends on its union with the oxygen in the blood-vessels, I will merely state the following experiments:--Carbonic acid gas was applied in a similar bottle, and in the same way, to the skin, the external air being excluded, and the skin moistened with water, for the space of ten minutes; but neither redness nor any sensible heat was induced; for this satisfactory reason, that heat is the consequence of oxidation with the carbon, which oxidation, in the case of carbonic acid gas, had of course been previously effected. _Alcohol_, _sulphuric ether_, _nitric ether_, and many other _ethers_--all of which contain a large portion of carbon--were similarly tried, but had no effect; for the same reason--viz. that it is already in a state of union with oxygen in all these highly carbonized bodies. I remain, Sir, your obedient servant, A. TURNBULL, M.D. CASE 1. _Opacity of the Cornea, the sequel of Small-pox._