NATURE 



[July 21, 1910 



run from the "Patch" to the African coast at Mogador. 

 Independently of the high land which is visible from the 

 sea at a distance of many miles, the approach to the 

 ■coast is indicated by a fall in the temperature of the 

 water of the sea surface, and a remarkable change in its 

 colour. Outside, the temperature of the surface water 

 was 21° C, and its colour was ultramarine. After sight- 

 ing^ the land its temperature fell, at first slowly, then 

 rapidly, and, when at a distance of two miles from 

 Mogador, it was only i6° C. The colour at the same time 

 had become a pure olive-green, which maintained its 

 transparency until close to the shore, where it became 

 masked by the solid matter kept continually in suspension 

 by the mechanical energy of the breaking waves. 



The pure green colour of the water and its tempera- 

 ture, so much lower than that which could persist at the 

 -■iurface of the sea in the latitude of Mogador, made me 

 for a moment think that it might be in reality Antarctic 

 water which had found its way, at or near the bottom, 

 into the northern hemisphere, having been diverted first 

 to, the west while in the South Atlantic, then to the east 

 after crossing the line. But this idea could persist only for 

 a moment, because the temperature and the density of the 

 bottom water were found to be those characteristic of the 

 bottom water of the eastern basin of the North Atlantic, as 

 shown by the Challenger observations, and these are much 

 higher than those of any other ocean. 



The low temperature of the water showed that it could 

 not_ come on the surface from the north or south or west 

 of it, and the only source from which it could come was 

 from below the surface. Deep water comes close to the 

 coast, and the water at 2000 fathoms was found to have 

 a temperature of 2-5° C, so that the supply of cold 

 from this source was adequate, and it was available 

 with a very small expenditure of energy. Arrived at the 

 surface and following the south-westerly drift of the 

 surface water, exposure to the sun raised the temperature 

 of the water and discharged its colour pari passu. It was 

 evident that there was here a case of the rising of deep 

 water at the weather coast of an ocean, away from which 

 the prevailing wind was continually driving the surface 

 water. 



From Mogador the Dacia proceeded to the " Seine 

 Bank," in lat. 33° 47' N., long. 14° i' W., and explored 

 it thoroughly. Among the specimens brought up on the 

 grapnel were masses of dead coral and shells, all baring 

 the same green colour. Some of these fragments were 

 preserved in spirit, which quickly assumed the green colour, 

 leaving the shells and coral practically decolourised. I 

 sent the bottle, with the specimens and. spirit, to mv 

 friend Prof. W. N. Hartley, in Dublin, who was good 

 enough to subject them to spectroscopic examination. He 

 wrote to me on February 15, 1884 : — " I have made a 

 spectroscopic exammation of the colouring matter vou sent 

 me and have no doubt that it is altered chlorophyll. I 

 have got identical wave-length measurements for the 

 abson-irion band with your liquid and a specimen of very 

 pure t..;t,.-ophylI dissolved in ether "; and he adds, " there 

 is very little real substance in even a dark green solution." 



As the year 1884 belongs now to the remote past, I 

 recalled the matter to Prof. Hartley, and, confirming his 

 previous information, he added : — " I believe my impression 

 at the time was that the chlorophyll was the colouring 

 matter in a living micro-organism, and that these settled 

 upon the shells, but when not deposited they were floating 

 in the sea water." I am obliged to Prof. Hartley for 

 kindly permitting me to use these private communications. 

 Further information will be found in his paper on chloro- 

 phyll from the deep sea (Proc. Roy. Soc. Edin., 1885, 

 xiii., 130). 



Prof. Hartley's report furnished a remarkable confirma- 

 tion of my first impression in so far as it showed that 

 the green water of the Mogador coast owed its colour to 

 the sarrie substance as did the diatom-crowded water of the 

 .Antarctic, namely, chlorophyll. 



In April and May of 1885 I made a coasting voyage 

 from Valparaiso to San Francisco. Excepting the equa- 

 torial part, stretching from Cape Blanco to Panama and 

 round the coast of Central America to near Mazatlan, the 

 west coast of the American continent between the fortieth 

 parallels is the weather shore of the Pacific Ocean. All 

 tilong it cold and green water is met with, in the same 

 NO. 2I2i^, VOL. 84] 



way as we have seen to be the case on the Atlantic coast 

 of Morocco. On the South .American coast the green 

 water was found to extend, with few interruptions, from 

 Valparaiso, lat. 33'' S., to Cape Blanco, lat. 4" 27' S. As 

 on the Morocco coast, the green colour and the low tempera- 

 ture of the water are found only close to the shore. At a 

 distance of ten miles outside the colour is blue, and the 

 temperature normal for the latitude. There can be little 

 doubt that, as the localities where the green water occurs 

 are geographically homologous, so the substance which 

 produces the colour is generically the same, namely, 

 chlorophyll. 



The following particulars are taken from my unpublished 

 journal. The only ports or anchorages where the water 

 was blue were Huasco, lat. 28° 27' S., temperature of the 

 surface water 14- 7° C, and Carizal, lat. 28° 5' S., tempera- 

 ture 15-1° C. The occurrence in this latitude of blue 

 water with so low a temperature is very remarkable. 



At .Antafogasta, lat. 23° 39' S., the water was greenish- 

 blue, and its temperature was i8-o° C. Between this port 

 and Iquique the ship's course took her to a distance of 

 nearly twenty miles from the coast, and there the colour 

 of the water was ultramarine and its temperature 2I-2'' C. 

 At Iquique the water was quite green, and its tempera- 

 . ture 17° C. Between this port and Arica the water was 

 quite green, even at a distance of five miles from the 

 coast, where the temperature was 19-5° C, but on anchor- 

 ing at Pisagua, lat. 19" 36' S., the temperature of the 

 water was only 15-2° C. At Arica, lat. 18° 28' S., the 

 water was equally green, but its temperature was I9'S° C. 

 Arica lies in the angle where the trend of the coast changes 

 from north to about north-west. From Arica the ship 

 made a longer run to Chala, lat. 15° 49' S., keeping at a 

 distance of fifteen to twenty miles from the coast. Here 

 ultramarine water was met with, its temperature 

 rising to 23>2° C, but even at fifteen miles from this 

 coast some green water was met with having a tempera- 

 ture of iSS° C. I attributed this to the foggy state ot the 

 atmosphere which prevailed. This obscured the sun, and 

 retarded both the heating and the bleaching of the water. 

 In lat. 14° 8' S., when six miles off shore, the water was 

 quite green, and Its temperature I5'i° C. Outside of 

 Callao, lat. 12° o' S., the water was green, and its tempera- 

 ture 16-3° C. ; in the harbour its temperature was 17-5° C, 

 and its colour a dirty green, turbid and milky with sulphur, 

 smelling strongly of sulphuretted hydrogen, and full of 

 dead fish. Continuing northwards, off Ferrol Islands, 

 lat. 9° 11' S., the temperature of the water was i6-o° C, 

 and its colour olive-green. At Payta, lat. 5° 5' S., the 

 temperature of the water was 17- 1° C, and its colour a 

 chalky green. , 



The green and cold shore water ceased abruptly at 

 Cape Blanco, lat. 4° 27' S., and during the passage round 

 this cape from Payta to the entrance of the Guayaquil 

 River, lat. 3° 9' S., the temperature of the water rose 

 from 17' 1° to 252° C. From this locality a pretty straight 

 line was followed across the equatorial current near its 

 source to Panama, lat. 9° o' N. During the passage the 

 ( temperature of the water varied between 25° and 27° C, 

 and it maintained a blue colour throughout. .At Panama, 

 however, with a temperature of 27° C, the w-ater was 

 quite green. 



\ similar occurrence of cold and green water near the 



shore was observed on the North American coast from 



Cape San Lucas, at the extremity of the Californian 



peninsula, to San Francisco. In the equatorial waters 



I which wash the coast from Cape Blanco, lat. 4° 27' S., 



to Panama, and thence to Cape Corrientes, lat. 20° 25' N., 



long. 105° 43' W., green water is prevalent along the 



I shore, but Its temperature is very high, 28° or 29" C. 



I Further information on this subject will be found in a 



• paper by me on similarities in the physical geography of 



the great oceans (Proceedings of the Royal Geographical 



Society, 1886, viii., p. 753). 



j I will here refer to only one other locality, and that a 



I well-known one, where the weather shore of an ocean is 



i associated with green water of abnormally low tempera- 



j ture. namely, the east coast of North .America from 



Florida to Nova Scotia. The cold and green water which 



' Is found on this coast, and lying between It and the 



western edge of the Gulf Stream, is usually attributed to 



' the Labrador current, which Is charged with the duty of 



