34 



SCIENCE. 



[Vol. YIII., No. 179 



courses in the bistory of political economy into our 

 colleges." And yet, at least as early as 1878, and I 

 believe for several years before that date, Professor 

 Dunbar gave at Harvard university an advanced 

 course in political economy, in vs'hich a large part of 

 the time was occupied with a careful examination of 

 the history and development of economic doctrines. 

 The writings of Adam Smith, Eicardo, and Maltbus 

 were naturally given especial attention. The course 

 of which this historical study was a part has con- 

 tinued to be given from year to year since it was first 

 instituted. Other institutions may also have offered 

 courses of the same kind ; but certainly in this 

 instance the history and literature of political economy 

 were studied before the new school had entered the 

 field. 



There is a tendency in the new school to claim for 

 itself perhaps an undue share of credit for the 

 advances in economic thought and economic teach- 

 ing which have taken place in the last ten or fifteen 

 years, — a tendency which seems to me to be illustrated 

 by Professor Ely's somewhat hasty remai'k. 



F. Vv^. Taussig. 



Newport, July 4. 



Sea-level and ocean-currents. 



In the number of Science of Jan. 1, I published 

 some notes on the great equatorial westward flow of 

 the earth's atmosphere and its influence upon oceanic 

 circulation. I credited to this great atmospheric cur- 

 rent the westward movement of the surface water 

 of the ocean beneath it, and considered the friction 

 of the winds as the most important factor in the 

 whole system of oceanic circulation. In an interest- 

 ing letter published in Science of Jan. 23, on sea- 

 level and ocean-currents, Mr. William Ferrel states 

 that the theory which attributes the movement of 

 ocean-currents to the friction of the winds is unten- 

 able, saying, among other things, " that it is well 

 known that ordinary winds have very little effect in 

 changing sea-level except in very shallow water." 

 He fortifies this assertion by quoting, from the re- 

 port of the chief of engineers, observations which 

 seem to show that the mean level of the water at 

 either end of Lake Ontario varies but one-third of 

 an inch with changes of wind ; that the sea level is 

 precisely the same on both sides of the Isthmus of 

 Darien ; and that the sea-level on the coast of Ireland 

 is the same in summer and v.dnter, though the more 

 violent westerly winds of winter should raise that' 

 level if winds were capable of moving and heaping 

 up water on a coast. 



Though fully appreciating the accuracy and value 

 of Mr. Ferrel's work, and differing from so high 

 authority with extreme reluctance, I deem it but 

 justice to myself to say that the question is by no 

 means so simple as he represents it, and that there 

 are many facts which prove, beyond all argument, 

 the power of wind to move great masses of water, 

 and to produce all the phenomena of oceanic circu- 

 lation. For example : for ten years I occupied in 

 summer a country house on an island in Lake Erie, 

 and I have more than once known a strong westerly 

 wind to depress the level of the water in the west 

 end of the lake, and raise it at Buffalo by two feet or 

 more. This means the actual transfer, within a 

 few hours, of a sheet of water of half the area of 

 Lake Erie, and one foot in thickness, fi-om the west- 

 ern to the eastern portion of the lake. 



I was once detained at Indianola, Tex., three 



days by a norther, which blew the water off the 

 coast till the harbor was almost dry land. 



Again : since this discussion began, violent south- 

 easterly gales have forced the ocean water into New 

 York harbor, and raised the water-level six feet or 

 more, inundating much of the lower portion of the 

 city, and causing great destruction of property. As 

 this rise was general along the coast, and was felt 

 as sensibly at Sandy Hook as at the Battery, it is 

 evident that we here have proof that wind is capa- 

 ble of moving vast bodies of water before it, even 

 where the depth is considerable. 



All the facts cited by Mr. Ferrel in support of his 

 statement are of equivocal bearing on this question. 

 The sea-level on the isthmus is still under discussion, 

 and, if it shall be proved to be the same on both 

 sides, that fact would be as difficulb of explanation 

 on the gravitation as the wind theory. 



Capt. John Brown of Put-in-Bay Island reports to 

 me that " a strong westerly wind sometimes de- 

 presses the water-level at Put in-Bay four feet below 

 the normal." And Mr. Julius Pohlman of Buffalo 

 writes me as follows : ''I learn from the records of 

 the signal office here that the heaviest south-west 

 storms on record raised the waters at this end of 

 the lake between eight and nine feet above the or- 

 dinary level. 



It is true that more violent winds are encountered 

 on the Atlantic in winter than in summer, but almost 

 none of these are continuous across the ocean. All 

 the cyclones are rotary, and the storms not such are 

 local and temporary. A change or reversal of direc- 

 tion of the wind would soon neutralize its effect, and 

 in winter the antagonistic easterly winds are cor- 

 respondingly violent on the European coast. On 

 the whole, it is doubtful whether the sum of the 

 impulses of the westerly wind is much greater in 

 winter than in summer. 



Since the atmosphere presses on the ocean with a 

 weight of nearly fifteen pounds to the square inch, 

 it is evident that when the air is moved the friction 

 must be great. This is demonstrated by the rapid 

 raising of ridges of water before a strong wind ; and 

 these ridges are all waves of translation. "Waves of 

 oscillation occur, but they are rare ; and the ap- 

 paratus so frequently employed for illustrating wave- 

 motion by vertical rods successively lifted is mis- 

 leading. 



Mr. Ferrel says, in conclusion, " A continuous 

 wind for some time in any direction causes merely 

 surface currents of considerable velocity;" but it 

 requires no argument to show that such surface 

 currents, if continuous, would infallibly produce a 

 movement of the deeper strata of water in the same 

 direction. 



The time estimated by Zoppritz for the transmis- 

 sion of surface motion to the depth of a hundred 

 metres seems to me grossly exaggerated : but even 

 if ten times longer than his estimates, the great 

 equatorial wind, which has doubtless been blowing 

 from east to west since the ocean has had an ex- 

 istence, would be amply sufficient to establish a 

 movement that would form a jmmum mobile for the 

 . whole system of oceauic circulation. 



That gravitation is a factor in oceanic circulation 

 is proven by the presence of ice-cold water in the 

 abysses of the ocean under the equator, — water that 

 must have flowed in from the polar regions, — but it 

 has seemed to me, and to many others whose opin- 

 ions are worth more than mine, that it is a much 



