A Canadian correspondent of _Nature_ gives a curious and interesting account of a phenomenon often to be seen on Lake Ontario during the prevalence of cold and stormy weather, such as the past season has afforded. ‘Ice volcanoes,’ as they are aptly named, are formed by an uneven strip of ice accumulating along the shore, on which appear mounds twenty or thirty feet in height. Many of these mounds are conical in form, and often have a crater-like opening, communicating with the water beneath. In stormy weather, every wave dashes spray and fragments of ice through this opening, which congeal upon the sides of the cone and add to its height; just in the same way that the fragments of pumice and other material ejected from a fiery volcano gradually build it up into a mountain. But the ice volcano soon becomes extinct, for the crater is gradually clogged up with ice, and the irruption can no longer find a vent. M. Trouvelet, who for the last nine years has been engaged in studying and mapping the configuration of the planet Mars, which, although not our nearest neighbour in the solar system, is that most conveniently situated for telescopic observation, has just presented a Report of his labours to the French Academy of Sciences. Sir W. Herschel long ago discovered that the polar patches of white on Mars increased and decreased in size in the winter and summer seasons of the planet, in the same manner as is experienced in the like regions of our own earth. Other observers have also mapped out the distant orb into regions of supposed land and sea, sometimes obscured by belts of cloud; moreover, the spectroscope has revealed to us, in its own wonderful way, the undoubted presence of water upon the planet. What are believed to be the continents of Mars are covered with faint grayish spots; and as these spots change their form and volume with the changes of the Martial seasons, M. Trouvelet supposes them to represent masses of vegetation which grow and die under the same solar influences which affect our own globe. Every contribution towards our knowledge of distant worlds—many of them proved to be so much greater than our own globe—must always have a fascinating interest for us.