SHEEP TICK AND ITS ERADICATION BY DIPPING. 31 



the groove into which the removable screen is to sit should be pro- 

 vided for, as well as the 4-inch openings for drain and outlet pipes. 



The trench for a cement* vat should be excavated so that the irjside 

 dimensions correspond with the outside dimensions of the vat when 

 completed. If the sides of the trench are smooth and reasonably 

 lii-m they can be used as the outer wall of the form, but in all cases 

 w here the vat is extended above the surface of the ground it is neces- 

 sary to build forms extending from the surface of the ground to the 

 top of the vat. If the soil is sandy it will be necessary to build outer 

 forms, in w^hich case the trench should be wide enough to allow for 

 these forms. The drain and other pipes shown in the drawing should 

 l)e placed in the form and should allbe threaded and capped so that 

 proper connections ma}' be made. The |-inch iron bolts and the iron 

 l^pe shown in the drawings should be embedded in the cement of the 

 incline for attaching the false iioor or crawling board. The floor is 

 made of 1 by 6 inch boards laid lengthAvise with cross cleats as shown 

 in drawings. The splashboards at the entrance end of the vat and 

 the guides at the exit end are nailed to 2 by 4 inch scantling bolted to 

 the cement wall, and the bolts should be embedded when the wall is 

 being constructed. Two pairs of bolts should also be embedded for at- 

 taching the slide board. Steam pipes should not be molded into the 

 concrete walls, as the vibration of the pipes will crack the cement. 

 They should pass over the top of the vat and down the side in a 

 groove formed in the wall, so they will not come in contact with the 

 sheep or cause annoyance to the men working along the vat. 



The walls should be made G inches thick, constructed of concrete 

 mixed in the proportion of 1 part cement, 2^ parts sand, and 4 parts 

 broken stone or gravel. This mixture is slushed into forms properly 

 set, and when it approaches dryness the forms are removed and the 

 inside surface of the vat coated with pure cement mixed to about 

 the consistency of cream and applied with a brush. It is important 

 that this coating be well brushed in so as to fill all ca.vities and form 

 ?. smooth surface. Finishing coats of sand and cement applied with 

 a trowel after the forms have been removed are liable to crack and 

 scale off. 



o 



