Feb. 15, 1 877 J 



NATURE 



333 



makes them unsuitable for insertion into a handle except where 

 the implement is small, and here the roughening is absent. I 

 also obtained a large number of the obsidian cores and flakes 

 from the Island of Melos, which are familiar to most collectors. 

 It is on these latter objects that I shall make some observations. 



On examining a series of these flakes I found a small number 

 of them which presented a singular wavy pattern down the back 

 ridge, which has evidently been produced by alternate pressure, 

 or a seiies of taps administered by some small instrument like a 

 punch.' I have since procured some more cores and flakes with 

 the view of examining the question more carefully, and have 

 been fortunate in securing some inteiesting evidence from them. 

 Out of a total of 230 obsidian flakes examined I have found 

 39 which have this marking with more or less distinctness. In 

 many cases the working is extremely rude, the alternate chipping 

 wide, straggling, and uneven, and the depth of the depression 

 and general character of the fracture such as to suggest con- 

 siderable violence in the blows which produced it. In other 

 cases the chipping is flatter and shallower, but still not very even. 

 But in a very few choice specimens the chipping is so even and 

 regular as to produce a pattern not unworthy of the manu- 

 factures of some of the "crimped" Danish daggers. 



On examining a series of small cores I was delighted to find on 

 a few of them traces which leave, no doubt that this curious 

 marking was produced before the flake was detached from the 

 core. In addition to the beautiful parallel fluting for which the 

 Greek cores are remarkable, I have found one ridge in some of 

 the cores (in 22 out of 125) worked up into the serrated edge and 

 ready for the blow which should have detached the flake. I have 

 only had the good fortune to find in one instance a flake still in 

 silu on its core whose chipping will compare with the best speci- 

 mens in my possession of detached flakes. Indeed on some of 

 the cores the working is so rude as to form merely a jagged and 

 irregular line instead of the beautifully clean ridge of the ordi- 

 nary flaking ; and without the evidence of the other flakes and 

 cores, I should not have been able to interpret the intention of 

 these ruder specimens. 



There is another form of working to be observed on a certain 

 number of the obsidian flakes. They have in many cases, by a 

 series of very delicate and flat chippings, had their back ridge so 

 modified or removed as to present a blade-like surface. In some 

 cases this extends over the whole of the back of the flake, in 

 others (where it has been a double-ridged flake) the chipping is 

 ir.erely enough to remove one ridge, making a blade like one of 

 our own dinner knives, thinner at the cutting edge than on 

 the blunt back. The intention in this case is very evident, being 

 merely to increase the cutting powers of the flake by removing all 

 impediments. Here again the chipping was effected while the 

 flake was still in situ. I have two or three cores with one side 

 flattened by the removal of several lidges, and awaiting conver- 

 sion into a knife-blade by a blow which never descended. 



The use, however, of the flakes with the serrated back ridge, 

 is more questionable. It is, I think, not possible to suppose 

 that tlie working in this case was put there as a mere piece of 

 ornamental cutlery, although the similar crimping on the Danish 

 daggers was certainly so. In the best Melian flakes the working 

 is certainly highly ornamental, but such specimens are some- 

 what exceptional, and in the majority of instances the working 

 cannot be considered ornamental at all, and evidently does not 

 aim at nicety and symmetry. Hence we may reasonably con- 

 clude that the purpose of the working was utility in the first 

 instance, and ornament only incidentally. I think there is little 

 doubt that these serrated flakes were manufactured to serve the 

 double purpose of a knife and a saw (rasp, or file), and they 

 would be by no means inefficient tools in experienced hands. 



I am not aware that attention has been called to thtse pecu- 

 liarities of the Greek obsidian flakes — or indeed that they have 

 been hitherto observed at all : and I have therefore thought it 

 worth while to offer some account of this interesting instance of 

 obsidian manufacture. I am not aware that any similarly worked 

 flakts have been discovered in Mexico ; and I should be much 

 interested if any of your readers could correct me on this point. 



It is worth remarking that there are several qualities of Greek 

 obsidian. The blackest and most beautiful is glossy and lustrous, 

 but will by no means compare with the obsidian of Mexico in 

 these particulars. Greek obsidian has nearly always an under- 

 tone of opaque green. There is, however, a quality which is a 

 dull kaden grey, slightly lustrous only, and less vitreous in its 



I Mr. John Evans, to whom I showed one of these, is of opinion that the 

 marking has been produced in the second of the two ways suggested, viz., 

 by blows administered by a small set or punch. 



composition. It breaks with the same fracture as the more 

 lustrous qualities. 



When the flake is trimmed very fine, it is frequently trans- 

 parent, and if held to a strong light presents a beautiful grey 

 and blick "brindled" texture. 



The Greek cores are all of small size, the longest which I have 

 seen being just under three inches ; but I have one flake which 

 measures 3f-, and a fe a^ which vary between that and three inches. 

 One most exceptional specimen, however, which is quite unlike 

 any of the others, and is weathered on both sides, measures 4^ 

 inches by i| broad, has a rough central ridge, a large bulb of 

 percussion, and is in sectional thickness % inch. I have some 

 shorter fragments approaching the same character. 



It will not have escaped the notice of many readers that Dr. 

 Schliemann found a number of obsidian " blades " (flakes, no 

 doubt) in one of the last opened of his tombs at Mykenos, together 

 with twenty- five arrow-heads of flint. Future discoveries in 

 Greece will furnish additional proofs of the general use of this 

 material in early times, and I have little doubt that Melos served 

 as the " Sheffreld" of Greece, in the obsidian trade. I had my- 

 self the fortune to pick up a small fragment of the substance 

 amongst the ruins of Tiryns. 



I have placed the series of flakes, cores, &c., in Charterhouse 

 Museum, wliere tUey can be seen by anyone who is interested in 

 them. Gerald S. Davies 



Charterhouse, Godalming 



Ocean and Atmospheric Currents 



In a clever article in the Quarterly Review, on the geo- 

 graphical and scientific results of the Arctic experlition, which I 

 have read with great interest, the following passage occurs : — 

 " Tiie polar streams flow southward as surface-currents as 

 long as they remain under the influence of northerly winds. 

 When they reach the region of south-westerly winds they 

 disappear under the warm waters of the Gulf Stream. And 

 this lor the simple reason that in each instance the stream, as 

 Sir George Nares says, will take the line of least resistance. In 

 the case of a stream going before the wind, this will be on the 

 surface ; when going against the wind, the line of least resistance 

 will be some distance below it." 



It is certainly very clever of ocean currents to dip below 

 the surface, when they meet with a foul wind, but that they 

 do so requires proof, especially as the warm current in the 

 North Atlantic, bound presumably from the equatorial to the 

 North Polar regions, makes a detour all along the north coast 

 of South America, deflected by the north-east trade when it 

 might apparently have accomplished its purpose so much more 

 directly by the simple expedient of dipping beneath the surface. 

 I would beg to suggest that the disappearance of the polar 

 streams under the warm waters of the Gulf Stream, as indicated 

 by the writer in the Quarterly, is to be accounted for in a far 

 simpler manner, viz., because owing to the high temperature of 

 the Gulf Stream in the latitude where this particular phenomenon 

 takes place, it is lighter than the fresher but far colder water 

 of the polar stream. 



While I regret to differ from Sir Geo. Nares, backed by so 

 great an authority as Mr. Croll, I must question the possibility 

 of wind piling up water to any great extent either on the surface 

 of the open ocean, or even in more confined water, of either 

 great or uniform depth, as the water will, under those circum- 

 stances, re-establish its equilibrium by running off below the 

 surface. 



We know that in both the polar and equatorial basins, we 

 have large volumes of water constantly running in at the bottom, 

 or in case some of my readers may disagree with me, with refer- 

 ence to the polar basins, I will put it more guardedly, and say 

 at some distance below the surface ; these currents must displace 

 on the surface a body of water exactly equal to their own 

 volume, and this body of water must necessarily run off in that 

 direction in which it meets the least resistance. For the sake of 

 brevity I leave out the consideration of evaporation and precipi- 

 tation, which bear a very small proportion to the large volume 

 of these currents. 



I have in a previous paper pointed out that " Heavier water flow- 

 ing continuously from a higher level {i.e., in the case of the ocean 

 from the surface) into the bottom of any basin of lighter water 

 must displace and raise a body of water equal to its own volume. 

 The lighter water will just as surely be lifted and buoyed upwards 

 by the heavier water as a ship, a piece of cork, or any other 

 substance having a less specific gravity than water, and when 



