540 



8CIEMCE. 



[Vol. VIII., No. 201 



should be conflicting opinions on this point. The 

 situation chosen, and the character of the work, 

 seem sufficient to place this conclusion beyond doubt. 

 Yet there are few, if any, satisfactory indications, 

 aside from the character and extent of the work, 

 that any portion of the enclosed area was occupied 

 for any considerable length of time as a village site. 

 That a work of such magnitude and extent could 

 have been hastily cast up for temporary protection 

 by a savage, or even by a semi-civilized people, is 

 incredible. Moreover, there are reasons for believ- 

 ing that the whole fort was not built at one period of 

 time, but was progressive. The southern part was 

 apparently built first, the northern section being a 

 subsequent addition, made possibly because of in- 

 crease in the population, most likely by the incom- 

 ing of parties or clans seeking protection. 



On the other hand, the evidences of long-continued 

 occupation, such as are seen in and about other 

 works, — as, for example, the Etowah and Messier 

 groups in Georgia, the Cahokia group in Illinois, 

 and several of the works in south-eastern Missouri, 

 — are wanting. This is also singularly true of 

 several other noted works of Ohio. The refuse 

 and cUbris of a populous village, occupying for a 

 long time a comparatively limited area, could not, as 

 is proven by the instances referred to, be entirely 

 dissipated by sixty years of cultivation, even though 

 carried on contintioiisly. The areas forming the 

 sites of some of the mound-builders' villages of 

 south-eastern Missouri, are yet, after half a century 

 of constant cultivation, a foot or more above the sur- 

 rounding level. 



What is the explanation of this singular fact ? I 

 can think of but one which seems at all satisfactory, 

 and that is, that these works were built by a populous 

 tribe, which was being pressed step by step before a 

 victorious foe. 



The defensive works of Ohio present to me no 

 evidences of great antiquity : indeed, the indications 

 are in the opposite direction ; and, in my opinion, 

 we are not warranted in assigning to them an age 

 antedating the latest possible period which we are 

 justified in fixing upon as that at which the Indians 

 first entered this territory. 



I give herewith a figure, from a sketch by Mr. 

 Holmes, showing that part of the wall which crosses 

 the field near the two mounds at the north-eastern 

 corner, including the part where the turnpike cuts 

 through, marked d by Squier and Davis. 



There is evidently a very great mistake in Dr. 

 Locke's estimate as to the amount of earth in the 

 embankment. If we take the length of the wall at 

 four and one-half miles, the average height at ten 

 feet, and the average base at thirty-five feet, the 

 volume is about 154,000 cubic yards, or less than one- 

 fourth the amount given by Dr. Locke, his estimate 

 being 628,800 cubic yards. If there is any error in 

 my figures, it is such as will overrun the true amount, 

 rather than fall below it. Cyeus Thomas. 



Milk-sickness. 



In the milk-sickness district, referred to in my 

 letter in Science of Nov. 26, the belief prevails, and 

 assertions are made, that the disease disappears so 

 soon as the land is cleared and cultivated, and some 

 cite instances where denuding the land of its forest- 

 growth has caused the disease to cease : so it may be 



set down as a fact, with considera le credibility, 

 that, as a general rule, clearing and (. iltivating the 

 land removes the cause of the disease, and any thing 

 to the contrary will be an exceptioi to the rule. 

 I can refer definitely to only one of these exceptions, 

 yet I have heard of a few others. Dr. W. S. Sims 

 of this place tells of a farmer in Hamburg township, 

 Jackson county, N.C., who has a half-acre lob en- 

 closed with his dwelling. In this enclosure are fruit- 

 trees and some of the native grasses, and the place 

 has been under cultivation for twenty years or more, 

 and yet whenever cattle are turned upon that lot 

 during grazing season they are sure to die with the 

 disease in a few days. From what I learned in 

 Macon county, N.C., if they were not practising on 

 my credulity, I am satisfied that that section will 

 afford isolated exceptions to the general rule. In the 

 lot above referred to, there is no water obtainable 

 except from a large creek of swift-running water, 

 that bounds one side of the lot. In that immediate 

 vicinity there is no milk-sickness outside the enclosed 

 half-acre. J. W. Walkeb. 



Pine Mountain, Ga., Dec. 2. 



A new mammal from the American triassic. 



In 1857, Professor Emmons (American geology, 

 part vi. p. 93) described the left lower jaw of a small 

 mammal from the Chatham coal-field in North 

 Carolina, naming it Dromatherium sylvestre. His 

 description was based upon one nearly perfect jaw 

 and two fractured specimens. The first, or type 

 specimen, is now in the geological museum of Wil- 

 liams college, and one of the others is in the collec- 

 tion of the Philadelphia academy. Through the 

 kindness of Prof. Samuel F. Clarke, I have recently 

 had an opportunity of comparing these rare speci- 

 mens, and find that the Philadelphia fossil belongs to 

 a genus quite distinct from Dromatherium, and unlike 

 any thing hitherto described by Professors Owen or 

 Marsh. The jaw is two thirds as long as that of 

 Dromatherium, and much more slender. The sym- 

 physial and angular portions are broken away. A 

 faint impression upon the matrix seems to indicate that 



the coronoid process was low. The lower border has a 

 downward process like that in Peramus. It is un- 

 certain whether the inner or outer aspect is upper- 

 most. The teeth are represented by two molars, 

 probably the second and fourth, and two so-called pre- 

 molars. The series as a whole occupy a greater 

 linear space than those of Dromatherium. The pre- 

 molars are simple, erect cusps, with a posterior basal 

 cusp. The molars give the principal character to 

 the jaw. Each has a central cone supporting two 

 smaller cones on its anterior and posterior slopes. 

 Hence, together with the slender character of the 

 jaw, the fossil may be called Microconodon tenuiros- 

 tris. In the drawing the dotted lines indicate the 

 probable shape and position of the four missing 

 molars. Henry F. Osborn. 



Princeton, N.J., Dec. 1. 



