346 



NATURE 



\_Mar. 5, 1874 



gresf elevations in different parts of the earth m'ght have 

 on the axi? of rntatiim. No doubt the removal of a large 

 qu.int'ty of solid matter from one part of the globe to 

 anothf-r wonld sensibly alter the principal axis, as well as 

 the axis of rotation, which so nearly coincides with it ; 

 but ir could bf -hown that it would produce in the latter 

 "nly ibou- i-30ith pirt of the change nroduced in the 

 form^-r. We kno.v t-io 11 tie of the changes in the interior 

 of the I arth accnmnanvina such changes on its surface to 

 be abl ;o t 'te re<iults with certainty. Bu' he estimated 

 that -in elevation, for examole, of 600 feet on a tract of 

 the earth's surface 1,000 miles square and 10 miles in 

 thickness would only alter the position of the principal 

 axis bv one-third of a seconii, or 34 feet. He called atten- 

 tion to the effect of tidal friction and subterranean vis- 

 cosiry in reducing,' any such deviation, and pointed out 

 that it must be exceedingly slow ; using for evidence the 

 observationally proved slowness of the diminution of the 

 earth's rotntional velocity, and of the inclination of its 

 equator to the ecliptic. It therefore seemed probable that 

 geological changes had not produced anv perceptible 

 change in the principal axis or in the axis of rotation 

 within the period of geological histor>'. 



OBSERVATIONS OF MAXIMUM AND MINI- 

 MUM SEA-TEMPERATURES BY CONTINU- 

 OUS IMMERSION 



WHEN the Scotch Meteorological Society was insti- 

 tuted, now nearly twenty years ago, observations 

 on sea-temperature were set on foot at the suggestion of 

 the late Prof. Fleming, and have since been continued. 

 These observations were made by the immersion of ther- 

 mometers with small cisterns attached, and were taken at 

 the surface and at a depth of 6 feet. Besides these, spe- 

 cial observations were made for me on the temperature of 

 the flood and ebb tide at depths extending to 50 feet 

 in the Pentland Frith,* and hourly observations con- 

 tinued at intervals during four years ending in .1S63 by 

 Capt. Thomas, R.N., at depths extending to 60 feet.f Sucii 

 occasional observations seemed to me to be insufficient to 

 show properly the changes in temperature to which the 

 sea is subject, and in August 1872 I suggested to my 

 friend, Prof. Wyville Thomson, the propriety of ascer- 

 taining, on his exploring voyage, maximum and minimum 

 temperatures by means of thermometers constantly im- 

 mersed in the sea. For this purpose a thin malle- 

 able iron plate of an oval shape, as shown in Fig. i, 

 is fixed to the outside skin of the ship so as to form a 

 small cell into which the sea-water finds ready ingress 

 through numerous perforations. This cell, which need 

 not project more than two inches, so as not to cause any 

 appreciable obstruction to the speed of the vessel, should 

 extend so far under the smooth water level as to pre- 

 vent its lower end from rising above the trough of the 

 sea, or an upright pipe might be placed within the vessel. 

 In sailing ships there might be a cell on each side so as 

 to secure constant immersion while the ship " is on a 

 wind." In this cell a frame carrying a maximum and 

 minimum thermometer slides in checks so as to be capa- 

 ble of being raised above water to the level of the cabin 

 or the deck, where there should be a porthole to admit of 

 the instruments being read and the indices being re- 

 adjusted. 



An arrangement similar in principle to that described 

 was made in the Challoiger exploring vessel before she 

 left on her voyage. 



In this way, during the whole of an over-sea voyage, 

 regular observations of maxima and minima may be ob- 

 'ained as often as may be desired. This arrangement is 



peculiarly suitable to floating lights, and the Scotch 



Meteorological Society have been in correspondence with 

 the Mersey Board in order to establish observations at 

 the North- West Lightship. 



The Marquis of Tweeddale in 1872 proposed that the 

 Scotch Meteorological Society should enter upon the 

 investigation of the migrations of fishes, and particularly 

 those of the herring, in connection with sea- temperatures 

 and weather generally, and his Lordship informed me that 

 in his opinion it was likely that the herrings followed belts 

 of water of a higher temperature than that of the sea 

 generally. 



In carrying out his Lordship's suggestion the Society 

 has been favoured through the courtesy of the Fishery 

 Board with returns of the daily catch of herrings and of 

 the weather from the different fishing districts of Scotland 

 fir the last two years ; and already two elaborate reports 

 on the subject have been drawn up by Mr. Buchan, 

 the Secretary, and published, which give good ground 

 to hope that some positive results of considerable im- 



portance will be obtained. With reference to this in- 

 vestigation, I suggested, for piers and harbours, the adop- 

 tion of a cast-iron pipe for containing the thermometer 

 as shown in Fig. 2, and application was accordingly 

 made to the Trustees of Peterhead harbour, where 

 observations by continuous immersion have been made 

 by Mr. William Boyd, F.R.S.E., since May 1873. It is 

 to be regretted that these observations have in the mean- 

 time been stopped, owing to a ship having come in 

 contact with the pipe. 



In addition to observations near the surface at floating 

 lights, it would be extremely desirable to have thermo- 

 meters immersed at greater depths, and for this purpose 

 a copper vessel weighted below should be used, as 

 represented in Fig. 3, with perforations in the upper 

 part and a cistern about 4 in. deep in the lower part. 

 The Scotch Meteorological Society, at its meeting on 

 February 9 last, authorized an application to the different 

 lighthouse authorities for sanctioning these deep-water 

 observations as well as those of the surface and of the air. 

 Thomas Stevenson. 



