18 



BULLETIN 376, U. S. DEPARTMENT OP AGEICULTURE. 



wax. Both the couphngs and attendant follow nuts were recessed 

 at an angle of 45° in order to effectively bind rubber gaskets. Joints 

 between ends of iron pipe units were made in the same way. A 

 cement made of equal parts of beeswax and turpentine softened the 

 rubber gaskets and gummed the pipe threads so that the joints were 

 mercury-tight. This was doubly assured by winding sewing thread 

 into the wax in the pipe threads. 



The inside of all metal pipes and connections was japanned three 

 coats thick in order to prevent amalgamation with the mercury. 



Color injector. — The only practicable method of measuring the 

 velocity of water in some of the pipes tested was by timing the passage 

 of some color or chemical. After various tests fluorescein appeared 

 to offer the best results. In order to inject the color into the pipe at 



the upstream gauge the "fluorescein gun" 

 was developed (fig. 3). This is connected 

 to the nipple C through the T connection 

 D. At the downstream manometer the 

 nipple C cotmects directly to the cock E. 

 Mercury container.— The usual lead tor- 

 pedo weights for the current meter were 

 dispensed with and a combination mer- 

 cury bottle and meter weight was con- 

 structed (fig. 3). The details are evident in 

 the illustration with the possible excep- 

 tion of the surge walls which divided the 

 bottle into small compartments so that the 

 mercury gave no trouble by surging when the bottle was used as a 

 meter weight. Likewise the small holes in the walls at the top of 

 the weight offered small chance of losing aU the mercury in case of 

 accident. 



FIELD METHODS. 



Mercury-^ 



Hmh Gage 



Dafu/n-'\ \ 



Fig. 2. — Hydraulic principles of mer- 

 cury maaometer of U-tube type. 



CHOOSING A REACH TO BE TESTED. 



In order to be considered adaptable for field tests, a pipe must be 

 practically water-tight (or the leaks measured) and of such length, 

 without bends or obstructions, that the effect of errors is minimized — 

 the longer the better. Gentle curves, both vertical and horizontal, 

 were thought desirable, as their effect must be considered in the 

 design of practically all wood-stave pipes. No distinct bend in any 

 pipe was included in the reaches tested. Such a bend would cause 

 an appreciable loss of head aside from friction loss. Some method 

 of determining the mean velocity in the pipe must be available. 



