A large extent of the desert in the north is covered with a prodigious lava-flood from a crater near the Fremrincvmar (Farther solfatara), while in the northwest it chiefly consists of outbursts of lava from huge rifts similar to the one that issued in the Myvatn's Orcefi in 1875, and a smaller one a few miles northeast of Hekla in 1878. The lava which has welled up in this manner is the newest looking and most rugged. The oldest lava that I saw appeared to be the surface of the last of the veritable oceans of molten rock which at one time overspread this portion of the interior of Iceland. We saw some of them, it will be remembered, bared by the rifts in the Mijvatn's Orcefi. Occasionally tracts of this are met with between the newer lava-floods, where the lava has congealed so evenly that its surface is as level as a paved footpath; and such places being swept clear of sand by the winds, the traveller's pony, which usually in this desolate region proceeds very spiritlessly, can be forced into a trot. I noticed also tracts where this old lava had formed innumerable flatfish dome-shaped bubbles starred with deep fissures, caused by the contraction of the mass when cooling", and as our ponies picked their way carefully over these, the sound of their hoofs striking against the rock rang hollow as if caverns were beneath, which is probably the case. Mostly, however, the spaces between the newer outbursts of lava have been filled in with sand-drifts in stormy weather, and it is possible to cross the desert by keeping to such places, skirting the newer lava-beds which are utterly impassable on horseback. It is toilsome work for the ponies as they sink fetlock deep into the sand at every step; and one is compelled to pursue a very circuitous route, skirting the rough lava-beds until it is possible to ride round them. Fortunately, the beds appear to lie above channels radiating from Ashja, and tend in the direction of the mountain; therefore in riding to and from that volcano one is not compelled to make such lengthy detours as would be necessary to cross from east to west. Both times that I have crossed we have headed as straight as possible for a gap in the highest part of the crater's mountainous periphery on the outward journey, and for the Sellandafjall, the westernmost of the mountains south of Myvatn, on the return. Only by the bearings of the mountains can the traveller direct his course, for compasses are totally unreliable by reason of the quantity of iron in the lava; therefore to be overtaken by a fog or a snowstorm, or worse still a sand-storm, when far out in the desert, would be a very serious matter, as under such circumstances it would be impossible to advance or return, and nothing could be done but await with all the patience at one's command for the fog to clear off, or for the storm's cessation. In the case of a fog or a sand-storm there would be no water, as only on the Dyngjufjdll, Trdlladyngja, and the other mountains, or immediately at the foot of their slopes, is it possible for the traveller or his steeds to quench their thirst, the streams from the glaciers and snowfields being absorbed by the arid sand and porous lava at the very bases of the mountains.

It will be evident from the above description of the OdaSahraun that it is not the most pleasant or safest region in the world through which to travel, especially as fogs, sand, and snow-storms of several days' duration are of frequent occurrence, even in summer, in this high latitude. Therefore, though it is only ten hours' ride from Svartcikot to the pass through the Dyngjufjoll into Askja, enterprising travellers who venture there are by no means sure when they will return; Professor Johnstrup's party when he visited the volcano in July, 1876, were snowed up in the crater by a snowstorm which lasted thirty-six hours, and made their escape therefrom with difficulty. Gunnlaugsson, as stated in the prefatory chapter, in the summer of 1837, when he made an excursion into the Odafiahraun to map out that portion of the island, was compelled by fogs and snowstorms to abandon his project, and only with the utmost difficulty made his way out of the desert to a farm. Three years later, a German, Schythe by name, visited Iceland and made light of the perils attending travel in the interior, as Burton has done since, and, like the ' veteran traveller,' he failed ' to plant his lance in Iceland,' which was no less an undertaking than to prove that it was an easy matter during the summer months to cross the interior from west to east by the route taken by Gunnlaugsson, being driven back by a severe snowstorm with the loss, it is said, of several ponies. Therefore, although seldom a decade passed away without a volcanic eruption in this fire-blasted storm-swept wilderness, it is hardly to be wondered at that no one was ever bold or curious enough to visit the spots where these took place until February, 1875, when an exceptional and adventurous Icelander, Jon, of Viftikcer-of whom more anon-crossed the Oddftahraun from Myvatn to Askja, in the coldest month of an Icelandic winter. There was another reason why the peasantry were loath to venture into the desert, they believed it to be peopled with a lawless race, the descendants of men outlawed in the middle ages, and that the sheep and ponies which frequently strayed away from the outlying pastures on the borders of the Oddftahraun, and were never more seen, were carried off by them. This summer, however, Jon, of V'&ikcer, induced several of the farmers living in the north to accompany him on an exploring expedition, with the object of ascertaining if there really was anyone living in the lava-desert, or whether there were any pastures to which the lost sheep and ponies strayed and there lived in a wild state. I was at ReyfcjahUb when Jon and his companions returned, and he told me they had passed ten days in the interior, and had thoroughly explored the region south of Myvatn between the two rivers, to the very base of the Vatna Johidl. They had found the skeletons of many sheep and ponies which had strayed into the dismal waste and there perished of starvation ; and also in a grassy oasis between the upper forks of the Jokulsd, the remains of an old house, built wholly of slabs of rock and lava without a particle of timber, the roof of which had long since fallen in. The bleached bones of sheep and ponies were lying around; therefore, in all probability this house was for some time the abode of outlaws, though possibly at least a century ago. Thus we see that there was some foundation for the belief of the country people that the descendants of outlaws were living in the desert, and that their live stock were stolen. It is to be regretted that no attempt was made by the exploring party to clear away the debris of the roof to ascertain if the skeleton of the ' last man ' remained in the house, where it is likely he perished unattended. This would have been no easy matter, Jon said, some of the slabs of rock that formerly roofed the house being so weighty that two men could not lift them.