April 22, 1887.J 



SCIENCE. 



393 



According to the view here presented . the follow- 

 ing are some of the actions and reactions taking 

 place in thunder-storms : — 



I''. There exists above the earth's surface strong 

 currents of air moving inward toward the central line 

 or area of the thunder-storm. This is attested by bal- 

 loon observations and bj^ observations of clouds. 



2°. There arises from the sudden expansion of air 

 entering the vortex of thunder-storms from beneath 

 a reaction which produces a compression of the air 

 near the earth's surface, and a rise of the barometer. 



3°. This compression causes the air near the 

 earth's surface to tend outward in all directions 

 from the centre of a thunder-storm ; but the outflow 

 in moving storms is only felt, or attains its greatest 

 strength, on the front of the storm, where the direc- 

 tion of the outflow is combined with the progressive 

 motion of the storm. In tornadoes the vortex usual- 

 ly reaches to the earth's surface, and there is no 

 place for a vertical reaction ; but where the vortex 

 is some distance above the earth's surface, there is 

 the same evidence of a straight outblowing wind 

 moving in the direction of the tornado, as there is in 

 a thunder-storm. 



4°. This rapidly outflowing current, by its dynamic 

 action on the barometer or its environment, fre- 

 quently or generally causes a depression of the 

 barometer in the front of thunder-storms, where the 

 outflow is most violent. H. Helm Clayton. 



Blue Hill meteor, observ., April 10. 



Snake and snake-like mounds in Minnesota. 



From time immemorial a certain mythical or super- 

 stitious interest has attached itself to the serpent — 

 the wisest of the beasts of the field — amongst most 

 nations, whether civilized or barbarous, and his pic- 

 tured or sculptured delineations have been the occa- 

 sion for much writing on the part of antiquarians. 

 In North America the creature has been depicted by 

 the ancient inhabitants in various ways ; as, for in- 

 stance, by carvings on rocks, by outline arrange- 

 ments of stones or bowlders placed on the ground, 

 and, more sparingly, by mounds of earth. The lat- 

 ter belong to the class of earth-works known as 

 'effigies,' of which the 'Great Serpent' of Adams 

 county, O., stands an unequalled representative. In- 

 deed, with the exception of this one, no mounds rej)- 

 resenting snakes have hitherto been delineated and 

 published, excej^t one or two somewhat dubious 

 specimens in Wisconsin. 



In the course of my surveys in Minnesota, I have 

 met with at least two such effigy-mounds, which, 

 with some others looking suspicioixsly like tadpoles, 

 I have drawn in plan for the engraver. They are 

 numbered and described as follows : — 



No. 1 is situated on the west side of St. Croix 

 Lake, on the town-site of Afton, Washington county. 

 The land here slopes toward the lake, and the Rattle- 

 snake lies just above high-water mark. The head is 

 5^ feet high, 88 feet long, and 56 feet wide at the 

 broadest point, which is also the highest, from which 

 it gradually descends to the body. Where the head 

 joins the body the embankment is 22 feet wide and 

 nearly 2^ feet high. The body is but slightly 

 curved. In the next 160 feet the width increases to 

 26 feet, but the height drops to 2 feet. From this 

 point it gradually diminishes to 18 feet in width and 

 1 foot in height. Connected with the extremity or 

 tail, there are three small mounds whose bases inter- 



lock, thus forming the rattles. The last of these 

 mounds is 20 feet long and 18 feet wide, and the two 

 between it and the tail are each 18 feet in diameter, 

 and all three are of the same height as the end of 

 the tail. The total length of this effigy is 534 feet. 

 On June 25, 1883, when this survey was made, in ad- 

 dition to the snake, there were four round mounds 

 and one embankment in the group. Formerly there 

 were other mounds, but they had been demolished. 



No. 2 is on the east side of Spring Creek, some 

 three miles westward from Red Wing. It has a per- 

 ceptible head, which is 8 feet wide and 1 foot high ; 

 the neck is nearly 7 feet wide and 10 inches in height. 

 From the latter point the body gradually increases 

 its width until the middle is reached, where it is 14 

 feet Avide and 2 feet high : thence it decreases to the 



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end of the tail, which is 8 feet wide and 1 foot high. 

 Its total length following the curves is 430 feet. The 

 mound which covers the body near the head is 52 

 feet in length, 36 feet wide, and 5 feet in height. 

 From general appearances it would seem that it was 

 built after the snake was constructed ; for the slope 

 of the mound where it strikes the body of the snake 

 is somewhat irregular, and indicates that its builders 

 were at a loss to know how to join them symmetri- 

 cally. These irregularities are not caused by the dirt 

 washing down from the top of the mound, for other- 

 wise it is perfectly symmetrical and the base well 

 defined. 



No. 3 is in another group of mounds about 250 

 yards down the same creek from the preceding one. 

 The head is circular in form, being 40 feet in diame- 

 ter and 3J feet high. The body at the junction with 



