INSTRUMENTS. 



191 



us for a time. Presently when our brains, addled by 

 sun and sickness, had recovered tone by a return to the 

 Usagara sanitarium, we remembered a rough and ready 

 succedaneum for instruments. I need scarcely tell 

 the reader that, unhappily for travellers, the only means 

 of ascertaining the longitude of a place is by finding 

 the difference between the local and Greenwich times, 

 and that this difference of time with certain corrections 

 is converted into distance of space. We split a 4 oz. 

 rifle-ball, inserted into it a string measuring 39 inches 

 from the point of suspension to the centre of the 

 weight, and fixed it by hammering the halves together. 

 The loose end of the cord was attached to a three- 

 edged file as a pivot, and this was lashed firmly to 

 the branch of a tree sheltered as much as possible 

 from the wind. Local time was ascertained with a 

 sextant by taking the altitude of a star or a planet ; 

 Greenwich time by a distance between the star or 

 planet and the moon, and the vibrations of our rude 

 pendulum did all that a watch could do, by register- 

 ing the seconds that elapsed between the several obser- 

 vations. 



I am somewhat presuming upon the subject, but per- 

 haps it may here be better to chronicle the accidents 

 which happened to the rest of our instruments. We 

 had two Schmalcalder's compasses (H. Barron & Co., 

 26, Oxenden Street), which, when the paste-board 

 faces had been acclimatized and no longer curled up 

 against their glasses, did good service : one of them was 

 trodden upon by my companion, the other by a sailor 

 during a cruise on the lake. We returned with a 

 single instrument, the gift of my old friend Lieut.- 

 General Monteith ; it had surveyed Persia, and out- 



