Messrs. Editors—It may not be generally understood by scientific men, bnt it is well known to dairy men and housewives that a violent thunderstorm turns sweet into sour milk. To ascertain whether electricity has any direct agency in producing this result, I passed a current of electricity from a Daniel battery of three cells through a bowl containing fresh milk, the connecting wires leading to and from the milk being copper. I enclose you so much of the terminal point of thcwire from the positive pole of the battery, as was immersed in the bowl. You will observe that it is encrusted with coagulated milk, through which is diffused a very perceptible quantity of sulphate of copper. The other end of the wire in the milk connected with the negative pole of the battery, and through which the current of electricity flowed from the milk, presented no such appearance—it was clear and unaffected. The only perceptible effect from this wire was a line of froth about half an inch broad, directly over the wire, and in the form of an S, similar to the bend of the wire, while no such effect was produced over the surface of the other wire. In three hours afterwards, this milk was tested with litmus paper, and compared with another dish of milk taken from the same source. No more acidity was shown by one than the other of these quantities of milk, and the cream rose with equal regularity on each. I therefore concluded that electricity has no direct agency in turning sweet into sour milk during a thunder storm. Is the agitation produced by the concussions of thunder storms the cause of milk souring? Do the discharges of artillery produce the same effect ? The specimen of the terminal point of the positive conducting wire shows that the current flowing into the milk through the copper wire formed sulphuric acid around it, by which the more solid portions of the milk (cheese and butter) were then collected, and a portion of the copper converted into a sulphate. . The experiment was several times repeated, and always with the same result. During the formation of the insrustation, a line of points was always thrown upward. When platinum was substituted for copper as the terminal point of the positive pole in the milk, no such effect was perceptible, as was seen with the copper. This was really but an initial experiment, which should be followed up by others who have more time to make them than Yours truly, J. D. Caton. Ottawa, 111., May, 1858. Two questions are asked in the foregoing communication regarding atmospheric agitations by thunder and artillery di charges, in causing milk to turn sour. We cannot answer them from practical observation, although it has long been known to us, and almost every other person we suppose, that milk is liable to become sour during thunder storms. We attribute this influence to the state of the atmosphere, not the thunder concussions, as it is well known that the weather is generally sultry or hot just prior to a thunder storm, and this warm condition of the air is very favorable to the development of lactic acid in the milk. It was this acid which, in the f oregoing experiments, united with a portion of the copper in the wire and formed the lactate, not the sulphate of copper, as mentioned, because there was no sulphuric acid present to form the sulphate We hope that such experiments will be extended by others, as recommended by our correspondent, for the field for investigation is interesting and expansive. [After the foregoing had been put in type, we received another letter from Judge Caton, in which he says that the above one was written in haste, and he omitted to state that in his opinion the sourness of milk caused during thunder storms was probably owing to the temperature and condition of the atmosphere, views which accord exactly with those we have expressed. We have noticed a paragraph in the columns of several of our cotemporaries, in which it is stated that some experiments had been made at Cincinnati with sweet milk, by passing currents of electricity through it, and that the butter by the operation was separated or churned in the most complete and perfect manner. Such statements are not worthy of the confidence of the above communication.]