740 SEC. 15. GEOGRAPHY. 



the common bearer, and the other to a special arm of the base piece at a 

 distance of 4 metres from the former. The comparator is also arranged, if de- 

 sired, for the comparison of the standard metre line measure (a traits} with a 

 yard end measure (a bout). For this purpose small cylinders with scales are 

 applied to the standard yard in order to compare suitable lines of these scales 

 with the metre ; then the sum of the lengths of the cylinders up lo the lines 

 of the scale employed is found by putting the two directly opposite one 

 another. The whole comparator is to be enclosed in a wooden case, in order 

 to keep the measuring rods at an equable temperature. 



3O93. Experimenting Model (quarter of the natural size) 

 for the preparation of bars for a new base-measuring apparatus. 



Carl B amber g, Berlin. 



The steel tube is bored through cylindrically in an axial direction, closed 

 at the ends and filled with mercury, which also passes into a glass tube, 

 closed above, and communicating with the bore. The height of the column 

 of mercury in the glass .tube will be a measure of the alteration of the length 

 of the scale by change of temperature. The proportions of the cavity of the 

 passage in the steel and glass tubes are so arranged that every change of 

 length in the scale is increased 100 times in the glass tube. 



This instrument has been made as an experiment by order of the Royal 

 Prussian Land Survey. 



3O93a. Drawing of a Base-measuring Apparatus, with 

 employment of the measuring bars mentioned with the above appa- 

 ratus. Carl B amber g, Berlin. 



1831a. Telescope, by Dollond. 



Sextant by Ramsden. Prof. Winnecke, Strasburg. 



Universal Instrument and Goniometer, by Robinson. 



Prof. Winnecke, Strasburg. 



The telescope is the " Dollond," so often mentioned in Humboldt's 

 account of his travels in America. 



The sextant and the universal instruments was taken by Humboldt in 

 all his journeys in Asia and America, and on the former depend nearly all the 

 determinations of position. It contains an inscription to this effect, and in 

 the case may still be found the paper in Humboldt's handwriting with 

 instructions for the engraver. 



These instruments form a portion of the Humboldt collection, with 

 which friends in Berlin enriched the new observatory of Strasburg, erected 

 in the year 1873. 



31O6a. Quadrant used by Captain Cook during his several 

 voyages. Richard Cauljield. 



3 O2 7. Instruments used by the late Dr. Livingstone in his 



last journey. The Royal Geographical Society of London. 



Pocket chronometer, by Jas. McCabe, 194, Royal Exchange, London. 

 Sextant, by John Dalton, of Hartlepool. 

 Hypsometrical boiling apparatus, by Casella. 

 2 boiling point thermometers, by Casella. 

 1 ordinary thermometer, by Casella. 



