of the Fishery Board for Scotland. 



413 



Tho course taken by the ' Jackal ' during the cruise, and the stations 

 or points at which observations were made, are given in the annexed 

 Chart of the North Sea. 



The nature and order of the work done at each station or point at 

 which observations were made was in general pretty much as follows : — 



1. The determination of the depth by means of a sounding line marked 

 in fathoms. This was frequently supplemented by Sir William Thomson's 

 sounding apparatus. The depths in fathoms as determined by this 

 apparatus are given in Table I. column XII., alongside of the depths 

 determined by means of the sounding line. Every care was taken to 

 ascertain the depth as accurately as possible, but the accuracy in each 

 case depends to a great extent on the absence of currents. At Station 

 XXVIII. special difficulties were experienced owing to this cause. 



2. The determination of the temperature of the sea water at the 

 surface and bottom, and at every 10 fathoms measured from the surface. 

 In some cases the temperatures at every 5 fathoms were observed. 

 The thermometers used in these determinations were, as on former 

 occasions, Negrctti and Zambra's reversing thermometers, fitted in 

 Scottish Marine Station frames. 



The thermometers were carefully compared on September 1st and again 

 on October 19th with a Kew standard thermometer, kindly lent by 

 Professor Tait. Between 0° C and 20° C the agreement was very satis- 

 factory. 



I have not applied any corrections to the observed temperatures, as I 

 much doubt the propriety of making corrections of less than a tenth of a 

 degree centigrade on observations made with these instruments. Through- 

 out the cruise these instruments worked admirably, and no loss or 

 breakage occurred. 



3. The collection of samples of water from the surface and bottom, 

 meaning by surface about 2 feet below the true surface, and by bottom 

 about 4 feet above the true bottom. 



4. The determination, when the conditions were favourable, of the depth 

 at which a white enamelled circular disk just ceased to be visible. 



5. The recording of the data given in Table I. columns I. to X. in- 

 clusive. 



During the intervals between one station and the other, and while lying 

 at the different ports, the following work was undertaken :■ — 



1. The determination of the alkalinity of the samples collected. 



2. The boiling out and collecting in hermetically-scaled glass tubes of 

 the gases from these samples. 



3. The determination, by means of a ' Challenger ' type hydrometer (No. 

 19), of the specific gravity of the samples. 



4. The careful preservation, in the manner described in a previous 

 report, of samples of the waters collected. 



Abridged Diary of the Cruise. 



Saturday, September I. — The work of the expedition began by the 

 conveyance on board and setting up of the various instruments and 

 laboratory fittings. It will be readily understood that apparatus employed 

 on such expeditions requires very careful adaptation to the peculiar con- 

 ditions which obtain on board ship. 



Monday, September 3. — A trial trip was made in the Forth to a point 

 a little beyond Inchkeith, where the instruments were tested, and the 

 methods of investigation rehearsed. Professor W. Dittmar, at my request 

 kindly'took part in this trial trip, in order that we might have the benefit 

 of his great experience in all matters connected with the chemical and 



