208 



POPULAR SCIENCE MONTHLY. 



which would be the most favorable time. His position on the wave 

 will be at S. If he is able to travel up the bay as fast as the wave he 

 will keep his position near the crest, that is at S. But he can hardly 



do that, especially as the cur- 

 rent would be very slight, and 

 in the broad bay hardly strong 

 enough for his guidance. Let 

 us suppose that by the time 

 he reaches Benicia, B, he has 

 fallen behind the wave until he 

 has the position at S'. It is 

 then slack low water, and he 

 can make no headway. Soon 

 the next wave reaches him and 

 he is in flood-tide. He will 

 therefore awim back against 

 the current. As the wave is 

 going up the bay and he is 

 going down, he soon gets past 

 the crest and finds himself in 

 the ebb-tide at S". He then 

 turns and stems the ebb-tide, 

 and as the wave is going in the 

 same direction he is, he goes 

 much beyond Benicia, B, be- 

 fore he again falls back to 

 slack low water at 8'", and 

 gets into the flood of the next 

 tide-wave. 



By taking the statistics of 

 the daily catch of salmon at 

 various points, we have been 

 able to trace the progress of a 

 school up stream, and find that 

 it requires four days to pass 

 from Vallejo to Sacramento. 

 We have been unable to de- 

 termine the length of time required to reach Vallejo after leaving the 

 ocean. 



The spring run passes up the river quite rapidly, reaching their 

 spawning grounds in the McCloud Eiver in about six weeks after enter- 

 ing the river at Collinsville. The fall run moves more slowly. The 

 flood and ebb tides are more nearly equal, owing to the small amount of 

 water coming from the rivers, which makes a longer passage through 



c* 



Map of Sacramento River and Outlet, showing 

 stations, by names or numbers, where salmon 

 inquiries have been made. 



