4i8 



SCIENCE. 



[Vol. XIII. No. 330 



Delaware, and has obtained stone implements from various points, 

 both personall)' and by interesting friends and residents in the work 

 he was engaged upon. He has also made a collection to show the 

 character and relation of the peat to the riveu'-deposits, and in vari- 

 ous ways has made a thorough study of the connection of the 

 river-stations with the early inhabitants of the shore. 



Mr. Cresson's investigations have also been carried on in relation 

 to the paleolithic implements found in the gravel, and he has been 

 so fortunate as to discover two specimens in situ in the older 

 gravel near Claymont, Newcastle County, Del. He also, in com- 

 pany with Mr. Thompson, made a visit to Indiana, and examined 

 the gravel on White River above Medora in Jackson County. Here 

 he was so fortunate as to find a large paleolithic implement of gray 

 ffint, in place in the gravel of the bluff of the east fork of White 

 River. A rudely chipped implement, probably of later date, was 

 also found in the gravel about a mile distant from the first, and ■ 

 was presented to the museum by Mr. Thompson. 



Mr. Cresson has prepared a full account, which will- soon be 

 printed, of the discovery of these implements. In the mean while 

 it is only necessary to call attention to the importance of these dis- 

 coveries in relation to the distribution of paleolithic man in Amer- 

 ica. The value of the material for this purpose cannot be over- 

 estimated, containing as it does nearly all the implements known 

 from the New Jersey gravels, in the Abbott and Lockwood collec- 

 tions, the two specimens from Delaware and one from Indiana in 

 the Cresson collection, the two from Ohio found by Dr. Metz, and 

 the Babbitt collection from Minnesota. For comparison with 

 these, the museum has numerous specimens from the gravels of 

 France and England. 



Professor Putnam's remarks on the results of his researches on 

 the Serpent Mound will be read with interest. He says, — 



" We have discovered many facts pointing conclusively to con- 

 siderable antiquity in the occupation of the region about the Ser- 

 pent Mound. We know historically that a hundred years ago the 

 region was inhabited by Indians, and we have found graves that 

 probably belong to that tim.e, or immediately preceding it, and we 

 have also found another class of burials having every indication of 

 far greater antiquity. Here upon the Serpent Mound Park, the 

 property of the museum, and not far from the Serpent, are three 

 burial-mounds with two entirely different methods of burial. Here 

 are a village site and a burial-place occupying the same area. A 

 recent and an early period are everywhere evident as the explora- 

 tion goes on. Every thing relating to the construction of the great 

 earthwork points to antiquity. The signs of the later occupation 

 of the region about it have nothing remarkable : simple ash-beds 

 where the dwellings stood ; burials in the black soil, with or with- 

 out protecting stones about the graves ; no elaborate structures or 

 indications of special ceremonies in connection with the burial of 

 the dead ; intrusive burials in a conical burial-mound ; — every 

 thing, on the one hand, pointing to a recent and not long-continued 

 abode upon the spot ; on the other hand, antiquity and special 

 ceremonies ; — a conical mound of considerable size, erected as a 

 monument over the body of a single person, buried after some 

 great ceremony in connection -with fire ; another mound under 

 which were four graves (one deep down in the clay under many 

 large stones ; three others over this, -with large stones about the 

 graves and over them, and a mound of earth over all) ; in another 

 instance a grave deep in the clay, with flat stones at the bottom, 

 upon which the body was placed, and over the body many large 

 stones, covered by the black soil of recent formation ; and in this 

 black soil, over the stones, a grave of the later period ; in another 

 place, under the black and recent soil, stones irregularly placed 

 upon the clay, marking graves, or places where fires were made ; 

 two and three feet under these once surface-piles of stones, the 

 graves, with skeletons so far decayed that only fragments could be 

 secured (in several instances only the outlines of the bones could 

 be traced in the clay ; in some cases the bones in part were pre- 

 served by the infiltration of iron, and the crevices in the clay about 

 the bones were filled with limonite, — all showing great antiquity 

 in contrast to the more recent burials). These older burials were 

 made in connection -with ceremonies during which fire played an 

 important part, as shown by the burial of ashes and burnt materials 

 with the bodies, and also by the stone fireplaces near the graves. 



In several of these ancient graves, objects were found similar to 

 tliose which we have obtained in the ancient mounds of other 

 parts of the State. In the recent graves, with the skeletons just 

 under the recent black soil, only now and then an arrow-point of 

 flint or a stone celt was found, with fragments of rude pottery, 

 such as are distributed over the surface of the village site. In the 

 ancient graves not a fragment of pottery was found. In one of 

 the oldest graves containing two skeletons were nearly fifty stone 

 implements and several ornaments, among them one cut out of a 

 crystal of galena. 



" Of the two periods, our explorations have shown that it can 

 hardly be questioned but that the Serpent Mound was built by the 

 people of the first, that it was connected with their beliefs and their 

 ceremonies, and that in its sacred precincts some of their dead were 

 buried. 



" This seems to be the legitimate conclusion reached by our 

 work to this time. I shall still have time for further explorations 

 before leaving this interesting spot, and there is much to be done 

 in the immediate vicinity another year." 



NOTES ON THE USE OF GRATINGS.i 

 The ghosts are very weak in most of my gratings. They are 

 scarcely visible in the lower orders of spectra, but increase in in- 

 tensity, as compared with the principal line, as the square of the 

 order of the spectrum : hence, to avoid them, obtain magnification 

 by increasing the focal distances instead of going to the higher 

 orders. The distances from the principal line in my gratings are 

 the same as the distances of the spectra from the image of the slit 

 when using a grating of 20 lines to the inch. They are always 

 symmetrical on the two sides, and about Jj of an inch for the violet 

 and i of an inch for the red in a grating of 31 feet 6 inches radius 

 in all orders of spectra. When the given line has the proper ex- 

 posure on the photographic plate, the ghosts will not show, but 

 over-exposure brings them out faintly in the third spectrum of a 

 20,000 grating or the sixth of a 10,000 one. They never cause any 

 trouble, as they are easily recognized and never appear in the solar 

 spectrum. In some cases the higher orders of ghosts are quite as 

 apparent as those of the first order. 



The gratings with 10,000 lines to the inch often have better defi- 

 nition than those of 20,000, as they take half the time to rule, and 

 they are quite as good for eye-observation. Tliey can also be 

 used for photographing the spectrum by absorbing the overlying 

 spectra, but there are very few materials which let through the 

 ultra-violet and absorb the longer wave-lengths. The 10,000 grat- 

 ings have the advantage, however, in the measurement of wave- 

 lengths by the overlapping spectra, although this method is un- 

 necessary since the completion of my map of the spectrum. By 

 far the best is to use a 20,000 grating, and observe down to the 

 D line by photography, using erythrosin plates from the F line 

 down to D. Below D, cyanine" plates can be used, although the 

 time of exposure is from ten to sixty minutes with a narrow slit. 

 The solar spectrum extends to wave-length 3,000, and the map 

 has been continued to this point. Beyond this, the coincidence 

 with the solar spectrum cannot be used, but those of the first and 

 second or second and third spectra can be. 



Some complaints have been made to me that one of my gratings 

 has no spectrum bej'ond 3,400, even of the electric arc. I have 

 never found this the case, as the one I use gives wave-length 2,200 

 readily with thirty minutes' exposure on slow plates, requiring five 

 minutes for the most sensitive part, and using the electric arc. 

 With sensitive plates, the time can be diminished to one-fifth of 

 this. 



For eye-observations, a very low power eye-piece of one or two 

 inches focus is best. This, with a focus of 21 feet 5 inches, is 

 equivalent to a plane grating with a telescope of a power of 100 or 

 200. 



In measuring the spectra, an ordinary dividing-engine, with 

 errors not greater than ^-^-^ of an inch, can be used, going over 

 the measurements twice with the plate reversed between the sepa- 

 rate series. The plates are on so very large a scale, that the micro- 

 scope must have a very low power. The one I use has a i-inch 



1 From Johns Hopkins University Circulars, May, 1S89. 



