there was any chance of a squeeze between the two ironclads, but now came manfully to the front and walked the rescued ship out into a safe position." THE ATLANTIC AND PACIFIC CANAL.-The surveys for a canal between the Atlantic and Pacific Ocean are now finished, and the problem becomes one for the capitalist and the engineer, instead of the explorer. Captain Shufeldt has returned home with an account of his labours on the Isthmus of Tehuantepec, and Captain Selfridge may soon be expected with details of his final examination of the Isthmus of Darien. In one of these two regions it seems to be the general impression that the canal must be built, if it is ever built at all the Nicaragua route, though not yet perfectly surveyed, attracting comparatively little attention. TO CORRESPONDENTS. We hope to insert the letter signed "Caleb Quoten" in our next. Staff-Commander Kiddle's paper we received too late for publication this month, it shall have attention in the September number. We beg to acknowledge the receipt of "Les Annales Hydrographiques," published by the Depôt des Cartes et Plans de la Marine, Paris, and we rejoice that the Department is resuming its activity now that the troubles of France are abating. We welcome a new comer in the cosmopolitan arena of literature. The "Nautical Gazette," of New York, has been in existence one month, and if we may judge from the contents of the early numbers which have been forwarded to us, it will not only benefit the spirited promoters of the new weekly, but will be of great service to the nautical community in general, and of America in particular. The new Edition of Mr. Thomas Stevenson's "Light-house Illumination," has been received; we shall notice it at length in our next number. THE AUTICAL MAGAZINE. NEW SERIES. SEPTEMBER, 1871. DEEP-SEA THERMOMETERS, BY CAPTAIN J. E. DAVIS, R.N., F.R.G.S. eprinted by permission of the Council of the Meteorological Society. Philip's encased maximum thermometers (Thomson's) being rely protected from any effect by compression, it was decided to rtain by their means the calorific effect produced by the sudden pression of the water in the cylinder; but, as will be seen by acing through the two series of experiments recorded, there was à a gradual increase in the temperature of the air, and also in water used for supplying the cylinder, that for any delicate. ervation, the conditions were not favourable; the observations calorific effect were therefore delayed until the weather got ler, when a more equable temperature could be ensured throughthe experiment. in order to ascertain what time it would require for these iniments to take up temperature (as it was of importance they uld not be kept under pressure longer than necessary) the foling observations were made, viz. :Compared two Thomson's thermometers (Nos. 9640 and 9647) the air with a delicate thermometer (No. 2528); all agreed. Placed the three thermometers nearly in a horizontal position in leep dish containing water (temperature 65.4°); when all agreed, the indices, replaced them in the water, the bulbs of the three VOL. I. 2 U being near together, poured in a little warm water at the furthest side from the bulbs, agitated the water with a pencil, and watched, with a magnifier, the effect. The mercury of the encased thermometers commenced rising almost as soon, and as quickly, as the plain, taking from one to three minutes to attain from two to three degrees, to the exact temperature of the water: this experiment was repeated several times and with the same results. Poured in a quantity of warm water with the following results. From 71.5 to 78.0 3.5 it took 0 15 = m. S. This was an outside period of time, or until a retrograde movement of the mercury was observed as the water cooled: it was therefore considered that five minutes would be sufficient time for the Thomson thermometers to take up the most minute portion of heat observable. For the purpose of observing this heat engendered by pressure, a Six's unprotected thermometer was made by direction of one of the Committee of the Royal Society, having the partially filled bulb open at the top, with a lip to which was firmly secured by wire a small piece of india-rubber tubing closed at the end, with the view of equalizing the pressure on both columns of mercury, and thus recording the amount of heat due to calorific effect only. A small portion of the mercury on the maximum side was oxidized; but it did not affect the reading, as it attained the same level on the scale of temperature as the minimum. November 12th.-The following observations were made, day cloudy, all the conditions favourable, Mr. Casella reading:No. 1. Pressure 2500 fathoms 6817 lbs. Under pressure = = Heard a crack at 1200 lbs. pressure; on taking the instruments |