XVI 



ccmsti'iictioii will in the case of low dams practically 

 place tlie moiitli of the lisliway in the line of the face of 

 the dam. 



In the case of high dams it will probably be better to 

 build the lishway with a return or elbow, so as to make 

 the discharge at the face of the dam. 



In the case of the Laurel Mills dam, there being no 

 surplus of water to deal Avith ordinarily, the tishway 

 may be made much narrower and the water discharge 

 proportionally reduced : a width of two or four feet for 

 the water wav would in this case be enoua:h. Such a 

 lishway would provide access to the upper waters of the 

 Patuxent for the salmon, the herrings and all the ana- 

 dromous or river species, except the shad'. I doubt if 

 the volume of water would be sufficient to induce the 

 ascent of the last named species in considerable numbers. 



I also examined the dam at the Relay House, on the 

 Patapsco. This is a timber dam about 7 feet high, and 

 is the first obstruction on the river above tide-water. 

 Tpon the dam there is now a crude lishway of the old 

 style. Iniilt by the ovrner, I presume, in conformity to 

 the requirements of the State law. 



It is not probable that the State will enter upon the 

 enforcement of a law making the erection of lishway s 

 obligatory, until their efficiency has been rested and 

 approved by your State Commission. 



The dam above mentioned furnishes an admirable 

 location for making the experimental tests required. 



I have therefore carefully examined the locality, and 

 submit to Tou the 2:eneral plan of a fishwav. such as I 

 think Avell adapted to meet the particular requirements 

 of the case, and if approved, will serve as a model for 

 subsequent constructions. 



The cost of this construction will be from five to eight 

 hundred dollars, varying with the cost of securing the 

 foundations on which to build the superstructure. 



Terv respectfullv vours. 



'M. Mcdonald. 



