Natural History of their Generation. 327 



(iJ) If the spring has not fall enough, you must raise a 

 ^ani round it, one or two feet higher than the top of your 

 trough ; convey the water from thence through a pipe or 

 gutter to the first grate in the opening on the head-part of 

 the trough, § I. (2), of one decimal square inch diameter, 

 and determine its length at least two inches above the grate; 

 the remaining water from the spring can be led oft" side- 

 ways. If you wish i6 have more breeding-troughs than 

 one, they should be fixed in the same directions as the 

 first; and a larger pipe must be put to the head of the 

 spring, which must empty itself into smaller pipes laid 

 across the water-trough, so that each trough may have its 

 proper quantity of water conveyed into it ; or it may be 

 managed by means of brass cocks ; but this is left to the 

 choice of every one's pleasure, as the most convenient me- 

 thod will be soon found out. 



(3) After the box or trough is properly finished, it must be 

 placed horizontally upon two legs of wood, stone, or brick; 

 and within upon its bottom put some clean-washed gravel 

 level, about the size of peas and beans, two inches high; 

 afterwards sprinkle some coarser gravel or pebbles over it, 

 the smallest of them of the size of beans, and some bigger 

 than hazel-nuts. This last is done, that upon the surface 

 of the smaller gravel many deep holes may be formed, to 

 prevent the continual motion of the water from carrying 

 away the eggs, it being necessary that they should remain 

 where ihcv were at first sprinkled in. 



(4) Then let the water nm into the trough as directed 

 hi (2), and raise it higher or lower according to the in- 

 structions in § I. (4), so that the water covers the gravel 

 always one or two inches. This being done, you have ac- 

 complished all that is necessary to the apparatus for breed- 

 ing trout and salmon. 



§111. 

 (1) The time of spawning begins the latter end of No- 

 vember, aqd commonly ends the latter end of January or 

 beginning of Februarv ; but the s))awning-time of each 

 trout continues only about eight days, as the eirgs of the 

 female and sperm of the male become in some sooner, in 

 others later, ripe. Trouis meet in rivulets in great numbers 

 in the belore-menlioned months; and such as are ready for 

 gpawnnig pitch upon a ])lace where there is lanje gravel, and 

 where the water has a quick current; there tlicy push and 

 rub their bellies against the stony bottom, and so violently 

 that they often make great holes ; and by means of this mo- 

 tion both male and female get rid of their spa\sn and sperm. 

 X 4 As 



