6 DR HUGH ROBERT MILL ON THE 



Si rival), was 42°0 on one occasion in February 1887, at 5 fathoms 42 0, 1, at 10 fathoms 

 44° - 4, at 15 fathoms 45 o- 0, and at the bottom (35 fathoms) 44 0, 1. Closer observations 

 showed that at 8 and 9 fathoms the temperature was 42° # 1, while at 9^ fathoms it was 

 44 0, 4, showing a rise of 2°-3 in 3 feet, and a change of only o, l in the 54 feet above. 

 In shallow estuaries almost all the change of temperature between surface and bottom 

 sometimes takes place in a few inches of depth. In such cases, Magnaghi's frame would 

 be of no service. 



Using a small boat, as I had frequently occasion to do, it is possible for the observer 

 alone — with a boatman to keep the vessel in position — to work a 120-fathom line, and 

 read the thermometers quite satisfactorily. It is convenient in such a case to use only 

 two thermometers. The first is set and placed a few feet above the lead, which may be 

 very light in still water, but must be heavy if there is a current, then lowered over the 

 side, and the second thermometer attached 5 or 10 fathoms or feet, as the case may be, 

 above the first. The second thermometer is set, and a messenger, previously clasped on 

 the line, hung to it by a wire or cord, the whole being then lowered to the proper depth. 

 The line is secured, and the interval of exposure may be taken advantage of for observ- 

 ing the air-temperature, at first with the dry-bulb sling-thermometer, if rain is not falling, 

 then with the wet. Three minutes having elapsed, a messenger is clasped on the line 

 and let go ; the impact is distinctly felt in a few seconds, and that of the second 

 messenger, released by the stroke of the first, is felt a little later. The line may then be 

 hauled up, the thermometers placed upright in the boat without being detached from 

 the line, then read carefully, set, and lowered again to different depths. 



On the " Medusa," on which most of the observations on the Clyde Sea Area were made, 

 the arrangements for taking soundings were convenient to the verge of luxury. A hemp 

 sounding-line, marked with coloured worsted at every five fathoms (and at every fathom 

 for the first ten), was coiled on a drum and passed through leading blocks to a tail block 

 on a derrick, which projected slightly over the port side near the bow, at a height of 8 

 feet from the deck. The ship was stopped, and one man stationed at the wheel, with the 

 engine reversing-gear within reach, kept her head to the sea with the line as nearty 

 perpendicular as possible on the windward side, so that the vessel could not drift over 

 the line. A slip water-bottle was fixed on the line, just above the lead ; two feet above 

 that — so as to be one fathom off the bottom — a thermometer was clamped on and a 

 messenger hung to it, in order to ultimately close the water-bottle. The whole was then 

 lowered ten fathoms, another thermometer and messenger attached, the process repeated 

 once, or twice if four thermometers were available, and the line was lowered until the lead 

 touched the bottom. In calm weather it was allowed to remain thus ; but when there 

 was any sea on, the depth was recorded, and the line raised one or two fathoms, to pre- 

 vent bumping. A messenger was let go after three minutes ; and as soon as the impact 

 of the last messenger on the water-bottle was felt, the steam winch rapidly hove up the 

 line. As each thermometer appeared it was removed, the winch being stopped a moment 

 for this purpose ; the reading could always be made and recorded by the time the next 



