Dr. Colan devoted much of his time to the investigation of the nature and causes of this disease, and I have no doubt his researches will throw a flood of light over this matter that will prove of the greatest value to succeeding expeditions in the preservation of their dogs, and be the means of baffling the attacks of this insidious disease. The dogs when employed in dragging a sledge are always harnessed in line abreast, and never, as generally supposed, ahead of each other in tandem fashion. From six to ten or a dozen dogs form a team. They are capable of dragging as much as one hundred and fifty pounds per dog; but this is rather an excessive load and should not be exacted for any length of time. So strong and enduring are they that they will frequently perform a journey, over smooth ice, of twenty-five or thirty miles a day with this load; but with light loads and level ice they have been known to travel as much as seventy and even a hundred miles in one day. There is something very exhilarating and exciting about dog sledging, so long as the weather is fine, temperature not too low, smooth level ice to travel over, and a light sledge to drag. But let all these various conditions be reversed, let the weather be thick and foggy, or a gale of wind blowing with a blinding snow-drift, a temperature of 50° below zero, rough hummocky ice to travel over, and a heavily laden sledge to be dragged by a tired and obstinate team, then dog sledging cannot be regarded as either a comfortable or desirable amusement. The sensation of dashing along on a light sledge at the rate of ten miles an hour, the fine snow flying into one's face as the dogs tear through it pell-mell in their headlong career, or perhaps plunging down the side of a steep ravine when the utmost caution is required to prevent the sledge from capsizing and toppling over on the top of the dogs, is both novel and delightful. But when obstacles such as hummocks and deep snow-drifts have to be encountered, especially with a low temperature, the reverse is the case. Directly the sledge receives the slightest check from either of these causes, the dogs lie down, and look at you in the most provoking manner. It is no use having recourse to the whip, for not all the flogging in the world will make them advance until the obstacle has been removed, or the sledge carried over the difficulties that had retarded its progress.