383 



observed when near the east and the other when near the west prime- 

 vertical. 



I also believe, from long experience, that the latitude of a place 

 may be ascertained by a few hours' work in a single clear night, 

 with the same apparatus and a good time-keeper — either a first qua- 

 lity pocket watch, or a chronometer — to withinone hundred or one 

 hundred and fifty yards of space, measured on the meridian ; that is 

 to say, to within 3" to 4". 5 of arc. This is quite near enough for 

 the projection of geographical maps, even on the largest scale usually 

 adopted. Even a nearer approximation often occurs from such 

 instruments and observations, by a few hours' work in a single night. 



By a series of observations on four pairs of stars, well chosen 

 under the rule before given — a condition that may often be secured in 

 two consecutive nights — the latitude may, we believe, be ascertained, 

 with such an apparatus, to within one second of arc. 



There is such a vast extent of our coimtry whose geography is 

 very imperfectly laid down, that this peculiar branch of practical 

 astronomy should be much encouraged amongst our countrymen who 

 travel either for purposes of scientific research, or for pleasure and 

 amusement. The requisite apparatus is easily transported, and may 

 be packed within the space of an ordinary travelling valise, excej)t 

 the time-keeper, which should essentially be carried in a wheeled 

 vehicle, either in hand, or on the person of the traveller. 



Sd. Observations for the Latitude of Milwaukee, 



These were made on the nights of the 1st and 6th of July, at sta- 

 tions No. 2 and No. 3, already described, as follows, viz. 



1858, July 1st. At Mihvaukee Station No. 2, in the middle of the 

 Court House Square. 



By 18 circum-meridian altitudes of £« Aquilce (Altair) ^ 



south, - - - - - 43 02 30.2 



By 12 altitudes of u Ursse Minoris (Polaris) north, 43 02 36.8 



Result — Latitude of station, by this night's observa- 

 tions, - - - - - 43 02 33.5 



Reduction to the steeple of the Roman Catholic 



Church on Jackson street, ... -f 0.29 



Latitude of this church steeple by this night's obser- 

 vations, - - - . - 43 02 33.79 



