HocKEN. — Abel Tasman and his Journal. 121 



sailors call a lunar distance. An improvement was made on 

 this cross-staff by adding one or two shorter transoms for read- 

 ing smaller angles. On some of those odd frontispieces which 

 embellish ancient atlases or geographies may be seen a sweet 

 little cherub holding aloft an emblem of the cross apparently, 

 but really this cross- staff. A hundred years after the in- 

 troduction of the cross-staff came Dr. Hadley's quadrant 

 (about 1731), which has developed into the perfect sextant of 

 to-dav. But with his tables of declinations, which were even 

 then calculated, and this simple instrument, Tasman and his 

 brethren succeeded in taking their latitudes with remarkable 

 accuracy, as is evident by inspecting the coast-line of his 

 Staten Land, which I have placed side by side with that of 

 our New Zealand. But how he succeeded with his longitudes 

 is quite a different matter. As we well know, longitudes can 

 only be calculated perfectly by knowing the difference of time 

 at two meridians, and this must be gained by the aid of accu- 

 rate timekeepers. In Tasman's day, the very few clocks and 

 watches in existence were but of little use in keeping the 

 time. The problem of longitudes at sea was always con- 

 sidered of the utmost importance amongst maritime nations. 

 Even at the begmning of this century it was thought that 

 it would never be solved, owing to the difficulty or impos- 

 sibility of ever constructing watches that would keep per- 

 fect time. As indicating this sentiment, the so-called Board 

 of Longitude advertised, at the beginning of last century, in 

 Queen Anne's reign, that they would give rewards of £10,000, 

 £20,000, and £30,000 respectively to him who should discover 

 a means of taking longitudes at sea to within sixty, forty, and 

 thirty geographical miles. Precision within these limits was 

 not thought of or expected. This liberal offer stimulated in- 

 vention, and Dr. John Harrison, an ingenious mechanician, 

 who for years devoted himself to making improvements in 

 clocks and watches, succeeded in 1764 in gaining the prize of 

 £20,000 with a watch — or chronometer, as we should now call 

 it — which was twice carried on a voyage to the West Indies. 

 The time kept was admirable, and insured an accuracy of 

 longitude to within ten or twelve miles. One of Harrison's 

 watches, which, by-the-by, cost from £80 to £100 apiece, 

 was carried by Captain Cook on his first great voyage of 

 discovery. Messrs. Wales and Bayly, who accompanied 

 Cook's second expedition, state, in their astronomical obser- 

 vations of the voyage, published in 1777, that the longitude 

 could then be computed to within the fifth or sixth of a 

 degree — that is, to ten or twelve geographical miles. The 

 earliest account I can discover of the use of timekeepers at 

 sea is in 1663, when two watches were used together on the 

 same vessel. The result was not satisfactory, as may be 



