384 



NATURE 



[Mar. 14, 1872 



young men who reckoned John Goodsir, Edward Forbes, 

 and many others of similar promise amongst their ranks. 

 On leaving Edinburgh he at once came to London, and 

 taking a house at the West End, attempted to establish 

 himself as a pure physician. During these eight or nine 

 years of his London life, Dr. Day laboured on with un- 

 wearying industry and patience,lecturingat theMiddlesex 

 and other metropolitan medical schools, writing for 

 reviews, Ir.mslating from German, and turning his ver- 

 satile talents and his special knowledge of physiological 

 chemistry to account in every way. The result of this 

 heavy strain was a threatening of brain disease, which, 

 according to the verdict of his medical advisers, could 

 only be warded off by complete rest and cessation from 

 the cares in which he was nnmersed. 



At that moment the death of an old friend. Dr. John 

 Reid, opened the prospect to him of obtaining the Chair 

 of Medicine at St. Andrews. His success in this probably 

 saved his life, for the removal from the turmoil of a 

 struggling London career to the compar.ative ea;e of the 

 Scottish University arrested the thrcatenings of disease, 

 and enabled him to recover some of his old vigorous tone. 

 Duringthei3years that Dr. Day held the Chair of Medicine 

 at St Andrews, from 1S50 to 1863, he made it his special 

 duty to promote the honour and further the interests of the 

 University by raising the character of medical degrees ; 

 and so successfully did he accomplish this task, that the 

 discredit which had belonged in former days to the M.D. 

 degree of St. Andrews was completely effaced under his 

 presidency of the Examining Board. Anew sjstem of 

 stringent I'/'i'd iioce and written examinations was then 

 inaugurated, which justified those who graduated in his 

 time in regarding their attainment of the M.L^. degree 

 of St. Andrews as a professional honour of which any 

 man might be proud. 



In 1S57 Dr. Day's prospects of a more prosperous future 

 than he had as yet been able to look forward to were 

 completely destroyed by the accident to which we have 

 already referred, and which befell him in the course of a 

 vacation tour in the English Lake Distiict. On a bright 

 morning at the end of the August of that year, he had set 

 forth front his hotel at Patterdale in full vigour and 

 strength, bent on "learning a new wrinkle about Hel- 

 \ellyn," as he himself expressed it, by making his way to 

 the summit along a recently opened path. He made the 

 ascent as he had designed, but instead of returning by 

 the same track, he struck off in the direction of the white 

 lead mines ; and while walking along what he mistook for 

 a miner's path, the ground gave way under him, and he 

 fell into what pro\ed to be a horizontal chimney or cul- 

 vert, constructed to carry off the sulphurous, arsenical, 

 and other gases, whose deposits had proved injurious to 

 the sheep grazing on the hill side. He was rescued afttr 

 three hours of anxious suspense, but the proximate results 

 of that accident were dislocation of the right elbow and 

 two fractuies of the same arm, the upper one in the 

 surgical neck of the bone of the humerus, which never 

 united. The subsequent effects were the complete de- 

 struction of his general health, which obliged him in 1863 

 to give up the Chair of Medicine at St. Andrews and 

 retire from active life. A removal to the milder climate of 

 Torquay had little cft'ect in arresting the train of symptoms 

 which 5 ear by year marked the progress of disease, and 

 were, it is conjectured, the result of a jar to the spine 

 sustained by his accident on Helvellyn, which had, in 

 truth, proved to him the beginning of the end. 



And such was the checkered career of this man of 

 brilliant promise, unflinching bravery of sphit, clear judg- 

 ment, and tender heart. Disappointed again and again, 

 he always met his troubles manfully, and turned them to 

 good account for himself or others. We have given no 

 list of the various honours which he attained in his pro- 

 ifession, or of his literary works, for the detailed reports of 

 these particulars are contained in the various obituary 



notices which have appeared of Dr. Day in the medical 

 and other journals, to whose pages, as well as to our own, 

 he was a frequent contributor. 



OCEAN CURRENTS 



A NEW interest seems now to be taken in Ocean Cur- 

 -^~*- rents, and much is being said and written upon the 

 subject. In the investigation of this subject it is very 

 important that we should understand well all the forces 

 and agencies concerned in the production and mainte- 

 nance of the currents, and that we should consider well 

 all the principles, and theories based upon hypothetical 

 forces, whicli have come down to us from preceding gene- 

 rations, however plausible and however much sanctioned 

 by high authority they appear to be. As in the case of 

 the winds, so also in ocean currents, the modifying force 

 arising from the earth's rotation has a very important 

 bearing, and should be well understood. There are cer- 

 tain erroneous views in connection with this force, which 

 have come down to us from preceding generations, and 

 which are contained in text-books, and are being taught 

 in colleges and schools, which are liable to have, and do 

 have, a mischievous beai'ing upon this subject. These 

 ai'e the more dangerous b;cause they appear to have 

 received at least the tacit sanction of past ages, so 

 that almost any one is liable to adopt them without 

 much consideration. Prof. Colding has in this way been 

 unsuspectingly let into error in his recent paper on ocean 

 currents. We are all familiar with the usual explanation 

 of the trade-winds contained in text-books, which assum- 

 ing that a particle of air at the equator, at rest relatively 

 to the earth, and consequently having a lineal velocity in 

 space of about 1,000 miles per hour, is forced to move to- 

 ward the pole, it will, on arriving at the parallel of latitude 

 where the earth's surface has a velocity of only 900 miles, 

 still have its velocity of 1,000 miles per hour in the case 

 of no friction, and consequently have -a relative velocity 

 of 100 miles per hour, and on arriving at the parallel of 

 60°, will still have its initial velocity of 1,000 miles, and 

 consequently have a relative velocity of 500 miles per 

 hour. But this is at variance with a fundamental and 

 well-established principle in mechanics. The force in this 

 case is a central force, or at least the compound perpen- 

 dicular to the earth's axis can be neglected, since it can 

 have nothing to do with any east or west motion. This 

 being the case, the principle of the preservation of areas 

 must be Satisfied, and consequently the particle of air, 

 when it arrives at the parallel where the earth's surface 

 has a velocity of 900 miles, must have a velocity of more 

 than 1,000 miles, and a relative velocity of more 

 than 200 miles per hour, and on arriving at the parallel 

 of 60^, where the earth's surface has a velocity of 500 

 miles, it must have a velocity of 2,000 miles, and conse- 

 quently a relative velocity of 1,500 miles, instead of 500 miles 

 per hour. Adopting thoughtlessly, and very naturally, the 

 erroneous principle which is usually taught, that a particle 

 of air or of water in moving toward or from the pole, tends 

 to keep its initial lineal velocity relative to space. Prof. 

 Colding estimates the amount of deflecting fjrce due to 

 the earth's rotation, eastward when the particle is moving 

 towards the pole, and westward when moving from the pole, 

 and the result is, that his force is just one half of what it 

 really is. Consequently, all the results based upon his 

 estimated amount of this force should be doubled. Prof. 

 Colding has also entirely neglected one component of the 

 force due to the earth's rotation. It has been shown by 



Prof. Everett, and also by the w riter, that when a body 

 moves east or west, there is also a similar deflecting force 

 due to the earth's rotation, exactly equal to the former. 



Prof. Colding has, therefore, taken into account only the 

 one-fourth part of the whole force. If he had taken in 

 this latter component of the force also, and resolved 



it in the direction of the line of motion and perpen- 



