378 



FORESTRY AND IRRIGATION 



August 



stick held horizontally against the tree 

 at arm's length, A H. The lines of 

 vision are tangents to the circle and cut 

 the measuring stick, B D, at B and C, 

 respectively. 



To construct the measuring stick for 

 certain diameters : 



A H, being the length of the out- 

 stretched arm, is known. 



When the length, B C, is found, it is 

 measured off on the stick, and the cor- 

 responding diameter is written at the 

 point C. In like manner, the ratios are 

 found for other diameters and marked 

 upon the measuring stick. It is obvious 

 that the ratios will differ as arms differ 

 in length, so that the same stick could 

 not be used by every one, but the sim- 



O F and O H, being radii of the circle 

 and equal to one-half of the given diam- 

 eter, are known. 



. . A O, being equal to A H 4- 

 O H, is known, and in the right-angled 

 triangle, A FO 



I 2 2 



= 



Since the right triangles A H C and 

 A F O are similar, 



HC:OF::AH:AF, OFXAH 



or H C = 

 and B C = 2 H C. 



/ * * 



\A O --O F 



plicity of the invention commends it, 

 because a measuring stick that will give 

 good practical results may be easily con- 

 structed within ten minutes to fit any 

 length of arm. 



Another idea of the inventor is to 

 apply the principle to the helve of an 

 axe, marking off the ratios as on the 

 measuring stick, so that the axe would 

 be useful, not only in marking and fell- 

 ing trees, but also have the added value 

 of being of decided use in measuring 

 their diameters to estimate their con- 

 tents. 



IRRIGATION FOR THE INDIANS. 



STUDY OF CONDITIONS IN THE GILA 

 VALLEY - - UNDERGROUND WATER SUP- 

 PLIES TO SUPPLY PRESENT DEFICIENCY 



THE underground waters of Gila 

 Valley, Arizona, have been re- 

 cently investigated by Mr. Willis T. 

 Lee, of the United States Geological 

 Survey. The object of the investiga- 

 tion was to ascertain the amount of 

 water available for irrigating the lands 

 of the Indians in this valley. The 

 greater part of the valley is included 

 in the Pima Indian Reservation, on 



which there are about 7,870 Indians. 

 They are an intelligent, industrious 

 people, and until 1890 they were pros- 

 perous. From time immemorial their 

 irrigation canals had been supplied with 

 water from the Gila, but since 1890 the 

 diversion of the Gila waters above the 

 reservation by white settlers has caused 

 a shortage of water. The result is that 

 the area of lands cultivated by the In- 



