332 ANNUAL OF SCIENTIFIC DISCOVERY. 



mastodon. The others arc lighter colored, and much less dense. Coming 

 as they do from the bed of a river, it is impossible to determine how far they 

 were originally associated in the same geological formation. It is not impos- 

 sible that those first mentioned were from the same locality. 



The dimensions of the tibia of the megatherium from the Brazos indicate 

 that it must have belonged to a much larger animal than the one whose re- 

 mains are preserved in the museum of Madrid : thus, the circumference of 

 the bone around the lower extremity, without the fibula, is two feet seven 

 inches ; that of the Madrid specimen, with the fibula, is two feet six inches 

 and a quarter. The breadth of the Madrid specimen, with the fibula, is 

 twelve and a half inches, and that of the specimen from the Brazos river, 

 u'ithout the fibula, is thirteen inches. In North America the megatherium 

 has hitherto been found only in two localities, viz., Skiddoway Island on the 

 coast of Georgia, and on the banks of the Ashley river in South Carolina. 



ON THE MUD VOLCANOES OF THE COLORADO DESERT. 



The following is an abstract of a paper communicated to the California 

 Academy of Natural Science, by Dr. John Veatch, descriptive of a visit to 

 the Mud Volcanoes of the Colorado Desert, in the month of July, 1857. 

 Among the numerous objects in California inviting the investigation of the 

 scientific and the attention of the curious observer, none are more conspicu- 

 ous than the " Salses " or " Mud Volcanoes " of the Colorado Desert. Hid- 

 den amidst the burning sands of a frightful waste, few persons have had the 

 temerity to encounter the labor and risk of visiting them. Even the Indians, 

 inhabiting the border of this Western Sahara, do not willingly venture so 

 far into its midst, unless it be during the annual rains. At any other period, 

 to miss one of the few springs of brackish water, or to find the place occu- 

 pied by drifting sands a not unusual occurrence would entail the certainty 

 of the horrors of thirst, if not loss of life. From personal experience I can- 

 not blame the repugnance of the natives to visit a district, which, in addition 

 to its physical repulsiveness, they suppose to be the abode of dark and 

 malignant spirits. 



The striking peculiarities of this wild region are, however, too striking to 

 remain long unsubjected to thorough exploration. The entire desert is sup- 

 posed to have been the bed of a great brackish or fresh-water lake, and is 

 said to lay many feet below the level of the ocean. The part I lately visited 

 showed deep lacustrine deposits, inclosing, in myriads, the conchological 

 records of the former sea. 



It was in the month of July that I had occasion, in the progress of a min- 

 eralogical excursion, to visit one of the above-named Salses. It is situated 

 about one hundred and fifty miles from San Diego, and sixty miles, in a 

 north-easterly direction, from the Indian village of San Felipe the nearest 

 inhabited habitable place. 



Starting from the above-named village, with an Indian guide, and horses 

 carrying provisions and water, the route for two days lay for the most part 

 over a desert track of sands and clays, thickly covered in some places with 

 forest of prickly cacti. On the morning of the third day, the white clouds 

 of steam arising from the Salse became apparent at a distance of about ten 

 miles, while the dull roar of the eruption could occasionally be heard. Ap- 

 proaching on horseback as near as was prudent, Dr. V. dismounted, and 

 proceeded on foot, over a soft and muddy ground, to the Satses. The scene 



