MR. HARTWELL CONDER wrote: - The author's description of the equipment of a mine-rescue station is full of interest and apart from its technical value serves to emphasize the need of every preparation against the contingency of fire. The writer had the opportunity of taking part in some of the rescue work on the occasion of the fire at North Mount Lyell and was especially concerned with animal tests for the presence of CO. The safeguards ensured by this means appeared so great that it seems to him that systematic provision should be made on those lines at every central station. A brief description of the methods arrived at may be of interest. The animals mentioned by Haldane in his "Methods of Air Analysis" were the mouse and small bird, such as canary or linnet. White mice were, he believed, employed on submarines. The children around Lyell did not seem to pursue the cult of the white mouse and cage birds were also scarce, so that when the writer wished to take some small animal into the mine, there seemed to be none available. The sight of some half grown fowls caused a start to be made with them and the descent and safe return of a young rooster from the main shaft helped in showing that the gases there were not too virulent. It was next found that week-old chickens could be obtained and a supply was secured. They were first used in cages, and the withdrawal of one practically moribund after five minutes at the bottom of the engine winze gave warning not to advance there too recklessly.