The Pioneer Alidade 



This alidade, as designed for W. H. Boyd, Can. Geol. Sur- 

 vey, is a replica of our standard model reduced in size and weight 

 about one-third. The base plate is 12 in. long, the arc has a radius 

 of 45 mm and the inverting telescope is usually furnished with 25 

 mm aperture and 16 magnifications. 



Like all our alidades the diapragm is furnished with the stadia 

 wires without additional charge. Whatever may be said of the 

 achievements and possibilities of the stadia principle, it is always 

 understood to be accurate up to the requirements of average plane 

 table work. 



For those who prefer the gradienter method, however, we have 

 also supplied, with this and with the next described instrument, 

 a gradienter drum with celluloid index as specified by Eugene 

 Stebbinger, U. S. G. S. (See top of p. 1 2 



This alidade, in connection with our No. 84 Traverse Tripod, is 

 highly recommended for mountian reconnoissance and for economic 

 railroad location. On prairie land, ten miles a day has been encom- 

 passed on contour work. In Eng. Rec., July 20, 1912, Prof. E. L. 

 Griggs, Univ. of Ga., reports on the use of the plane table for 

 highway construction and extensive relocation. 



The Miniature Alidade 



Manufactured exclusively by the B. & L. O. Co. 



rig. 34 



In Economic Geolo, Vol. VII, No. 7, 1912, C. H. Wege- 

 mann says, "A very compart telescopic instrument is that known 

 as the Gale Alidade, which was planned by H. S. Gale, U. S. G. S. 

 in 1909 and is unexcelled where a light compact instrument is 

 required." 



The arc is one of 120 duration, numbered from to 60 each 

 side of a center index, but on account of the absence of a 3^-in. 

 pillar, such as is used with the Pioneer type, not all of the arc can 

 be used. The ocular and objective mounts strike the plate at 18 



