The winter was passed in preparation for the next spring expeditions, for during the long Arctic night the darkness prevents travelling, and the snow acquires a peculiar hardness or sharpness from the extreme cold, so that then four times the number of dogs would be needed. But as in summer the thawing is likewise a hindrance, Wrangell had in reality only about ten weeks every year, from March till the end of May, for the accomplishment of his task. As may easily be supposed, it was no easy matter to make the necessary arrangements for an expedition requiring some hundreds of dogs, and provisions for several weeks; but such was the energy displayed by Wrangell and his colleagues, that on February 19, 1821, they were able to start on their first journey over the ice of the Polar Sea, which they reached on the 25th. Nine sledges, with the usual team of twelve dogs to each, were provided for the present excursion, six of which were to carry provisions and stores, to be distributed in different dépôts, and then to return. The provisions for the dogs consisted of 2400 fresh herrings, and as much “jukola” as was equivalent to 8150 dried herrings. The increasing cold and the violence of the wind made travelling very difficult. To guard the dogs from being frozen, the drivers were obliged to put clothing on their bodies, and a kind of boots on their feet, which greatly impeded their running. At times the frost was so intense that the mercury congealed while Wrangell was making his observations. He thus describes the manner in which he passed the nights on the Polar Sea in his tent:--