7H 



TEE POPULAR SCIENCE MONTHLY. 



of the ground. It is perhaps enough to say 

 that the coal measures to which coal is con- 

 fined in Arkansas lie far to the north of Hot 

 Springs, and that the hot waters come up 

 through Silurian rocks which contain no coal. 

 Of the theory that heat may be produced by 

 chemical action, it may be said that the 

 water itself gives no evidence of its having 

 received its heat in this way, its chief for- 

 eign constituent being carbonate of lime. 

 So far as the geology of the region is con- 

 cerned, if there were no hot water in the 

 vicinity none would have been anticipated 

 on geologic grounds alone. Notwithstanding 

 a writer at the beginning of the century men- 

 tioned having seen a volcanic outburst and 

 streams of molten rock near Hot Springs, there 

 is no evidence of such recent eruptive action, 

 which could not have taken place without 

 leaving readily recognizable traces. There 

 are, however, eruptive rocks near Hot Springs, 

 although they certainly were not thrown up 

 during the last hundred years ; and it is 

 probable that the heat of the water is de- 

 rived from its having come in contact with 

 hot rocks, the cool edges of which may or 

 may not be exposed at the surface. 



Ancient Outlet of the Great Lakes. — 



Among the latest geological observations of 

 Prof. G. F. Wright is the discovery of a for- 

 mer outlet of the Great Lakes through Lake 

 Nipissing and the Mattawa River to the 

 Ottawa. It has long been recognized that an 

 elevation of less than fifty feet at Niagara 

 or a depression of an equal amount at Chi- 

 cago would cause the lake waters to flow 

 into the Mississippi instead of the St. Law- 

 rence. Recent railroad surveys have further 

 shown that a subsidence amounting to only a 

 trifle more than a hundred feet would turn 

 the current from Lake Huron through Lake 

 Nipissing and the course already mentioned. 

 Prof. Wright has discovered evidence that 

 this condition at one time prevailed. Lake 

 Nipissing is scarcely seventy feet above Lake 

 Huron, and empties into it through French 

 River. The western extremity of Trout 

 Lake, the source of the Mattawa, is less 

 than three miles from North Bay on Lake 

 Nipissing, and is separated by a wide, 

 swampy channel which is only about twenty- 

 five feet above the level of either lake. It 

 is large enough to conduct the waters of the 



Great Lakes over into the present water-shed 

 of the Ottawa when called upon to do so. 

 " On looking for more positive evidence, we 

 find it in a clearly defined shore-line of well- 

 rounded pebbles extending upon the north side 

 of the channel from one lake to the other, 

 and at a uniform height of about fifty feet 

 above the connecting channel. This shore- 

 line is as well defined as that on the banks 

 of the Niagara River, just west of the pres- 

 ent cataract. Such a deposit could not have 

 been formed along this connecting depres- 

 sion except by a stream of vast size passing 

 from Lake Nipissing into the Mattawa. It 

 is, however, on going down to the junction 

 of this outlet with the Ottawa that the most 

 positive and striking evidence is seen. For 

 ten miles above the junction signs of the old 

 river terraces are more or less visible high 

 above the present stream ; but at the junc- 

 tion there is an accumulation of river depos- 

 its, unparalleled, probably, by anything else in 

 the world. The lower angle of the junction 

 between the two streams is filled to a height 

 of eighty feet or more above the present 

 water level with a bowlder-bed about half a 

 mile in width, and extending up the Matta- 

 wa for nearly a mile, where it shades off 

 into finer material. On the upper angle the 

 Mattawa is bordered by a terrace equally 

 high, but consisting for the most part of fine 

 gravel." The accumulation is clearly a ter- 

 race and not a simple glacial moraine ; and 

 that it is a delta brought down by the Matta- 

 wa and not by the Ottawa is shown by the 

 fact that it has dammed the latter stream, 

 producing in it deep water above and rapids 

 below, according to the well-known law of 

 river bars. 



Traveling and Camping in Egypt. — Dr. 



Frederick Peterson, of this city, recommends 

 winter camping in Egypt as a hygienic meas- 

 ure. He finds it something luxurious, and 

 says : " I have camped out on shooting expe- 

 ditions in Nebraska, Dakota, and other West- 

 ern places, and endured hardships that I 

 should not care to experience again. But in 

 Egypt, where labor and carrying cost next to 

 nothing, where everything in the way of 

 furniture and supplies can be stored away 

 somewhere on a camel ; where every day 

 can be foreseen to be rainless and beautiful, 

 life in tents becomes a pleasure. It is al- 



