^r.\r;xETTr sfrvet of japan', 220 



wns insîtriictof] to snrvoy all tlio Pc^nsts flivl inlands of Japfiii. Tlio 

 survey of tlie north -eastern coast was finished in 1801. and ])v LS IS 

 liis labours in the field were eonipleted. It shoidd l)e mentioned, 

 perhaps, that certain [)arts of the coast were surveyed very ini])erfectlv 

 — such as the eastern and the north-Avestern coasts. Exactlv wlien 

 he died is not known certainly, hut for some time after the comj)le- 

 tion of the survey he seems to have been eno-ao-ed in the construction 

 of his maps. 



The instruments which Inö employed in the survey were des- 

 troyed by fire ; but in 1828 two instruments, said to be exact copies 

 of the original ones, were made by Ono Yasaburo, the father (^f tlie 

 Jate engineer who constructed the Mint at Osaka. These are now in 

 the possession of the Meteorological Office. A compass-needle, made 

 and used by Inö, has however been preserved l)y his family. 



Ono's instruments are two, one for measuring azimuths and the 

 other for measurini'" altitudes. The former is simply a horizontal 

 circular disc of copper 19 inches in diameter, graduated by radial lines 

 into degrees. Seven concentric circles are traced near the extremity 

 of the disk at such distances apart that, when a straight line is en- 

 graved joining the point where the inmost circle cuts a given radial 

 line to the [)oint where the outmost circle cuts the next radial line, 

 this so-called diai^'onal ö-ives bv its intersections with the intermediate 

 circles anuular intervals correspondins; to 10' or one-sixth of a desfree. 

 The graduated circtdar disc rests on three legs j>rovided with levelling 

 screws. From its centre rises an upright wooden pillar which is siu'- 

 mounted by a tid)e (or })erhaps a telescope) for sighting distant 

 objects. The levelling of the circle is accomplished by means of a 

 brass "plummet" hanging down one side of the upright pillar. The 

 pillar rotates freely, and carries with it a horizontal rod resting on the 

 graduated circle. The positioTi of this r<-)d indi(\ates at once the angle 

 to be read. 



