I will here remark that, since the first edition, I have had occasion to use large quantities of soluble cotton, and have found that if it be kept in an atmosphere of alcohol and ether, its solubility is somewhat improved: that is, in the case of its not being used immediately after its preparation. This is easily kept, by dropping a few drops of ether or alcohol into the bottle containing it, and then sealing close until wanted for use. In the event of the water being displaced by alcohol, it is not necessary to thoroughly dry it, but put in a _perfectly close_ bottle to keep. _Remarks._--There are a few precautions necessary to be observed in the preparation of soluble cotton. I should select a fine clear day, if time is no object; nevertheless I have made a good article in a moderately dense atmosphere. Sulphuric acid has a powerful affinity for hydrogen, consequently, in damp weather, it is more or less reduced by the moisture in the air. It is advisable to prepare the nitro-sulphuric acid mixture on a roof, or between two doors or windows, where there is a good current of air, in order to prevent the inhalation of white vapors which arise, and are very poisonous to the lungs. As a preventive, in case of inhaling these vapors, I apply the fumes of aqua-ammonia. It is best for every one to have six or eight ounces of this always at hand; it neutralizes all acid that maybe spattered on the clothes, prevents its destructive powers, and restores the color. Yellow vapors sometimes appear when putting the cotton in contact with the solution: this arises from its not being wet; and when they do appear, the cotton where they are should be quickly put under the liquid and kneaded rapidly, which will prevent a continuance of these vapors. I have had them appear, and used the cotton, and could not observe that any bad effect had been produced. The temperature is worthy the attention of the operator: if it be low, as in winter, and the cotton be left in the nitro-sulphuric mixture for fifteen or twenty minutes, the whole becomes a thick, stiff mass, bedded together, and has not had proper action, giving a bad article. A good temperature is about 140° Fahr. for the last of the time the cotton is in the mixture. This is not always convenient; so the operator will be governed by circumstances, taking his chance of having a good article. In some cases I have heated a _thick_ iron plate, at a moderate temperature, placing the mortar upon it, and thus aided in regulating the temperature. This is the most convenient method I have employed. It has been thought advisable to publish in full the account of Edw. Ash Hadow's experiments and investigations upon the subject of soluble cotton. The following is an account of them as it appeared in _Humphrey's Journal_, vol. VI. p. 12:--