62 



. (6.) The latitude having been found for the initial point of a survey, it may be 

 found for other points within moth-rate limits by allowing '>- chains of northing or 

 southing for 1' of latitude. 



7.) The object of bringing the main telescope into the meridian by means of 

 motion on the outer spindle is to have the zero line of the horizontal plate in the 

 meridian, so that the azimuth or bearing of lines can be referred to that line. 



(8.) If for any cause one is obliged to work with an uncertain latitude, it is better 

 to ao so with the sun as far from the meridian as practicable, for the following 

 reasons: 



It is only when the sun is in the pole of the meridian that it has its maximum 

 efficiency in pointing out the direction of the meridian. 



Henoe a large hour-angle, and a small declination, are conducive to the elimination 

 of errors resulting from an incorrect latitude. 



Indeed, with the sun precisely in the pole of the meridian, the meridian is deter- 

 mined independently of latitude. 



i In making the several adjustments, or rather in verifying them, the student 

 should have a true meridian established by some other means than by the "solar 

 transit," as from the North Star, by some of the methods given in works on surveying. 

 II- should compare the results of his observations with this meridian at different 

 times in the day, and under different states of the atmosphere, till he has learned any 

 peculiarity of the instrument and the utmost precision obtainable with it, as well as the 

 ordinary limit of non-precision. 



Degree of Precision Required. 



(10.) This, of course, depends on the character of the work to be done. In the 

 U. S. Public Land Surveys, which are, without question, conducted on the best plan 

 the world can afford, only compass lines are required. As a consequence, a wide 

 margin for non-precision is given. 



In sub-dividing a block of townships, the surveyor in coursing a random of 6 

 miles, is required to make his objective point within 3 chains. Charging the half 

 of this error to lineal measurement, we find the error of coursing m::st be within l(y 

 of the true course. 



(11.) In Manitoba, the authorities, having fallen in love with our system 01 Pub- 

 lic Land Surveys, have adopted it; but they require greater precision. They re- 

 quire clear transit lines, projected with the best six-inch silver lined instruments, 

 graduated to 10". 



In coursing a 6 mile random in the sub-division of a township, the surveyor 

 must make his objective point within one chain, in order to save reviewing his work, 

 charging, as before, one half of this error to the lineal measurements, we find the 

 maximum error allowed in coursing to be between 3* and 4'. 



(12) With the " New Solar," as manufactured by Messrs. C. L. Berger & Sons, 

 the surveyor will be surprised and delighted to see the facility and certainty with 

 which he can brin'g his work far within the above limit. 



