Popular Science Moiillili/ 



36.5 



As the Water Passes 

 Down from the Top 

 of the Ladder It Flows 

 Through the Notches 

 in the Bottoms of 

 the Cross-Pieces into 

 the Next Lower Sec- 

 tions, Thus Making 

 Miniature Waterfalls 



water between an\- 

 cross-pieces finds a 



Iwo consecutnc 

 horizontal levc 

 determined by the depth of the notch in 

 the lower of the two pieces. As the 

 water passes down from the top of I he- 

 ladder it flows through the notches in the 

 bottoms of the cross-pieces and also 

 tlrops o\er the top notches in the cross- 

 pieces into the next lower sections like 

 small waterfalls. 



The water in the ladder is continualK' 

 flowing down and out at the bottom, 

 forming a running stream up which the 

 fish may swim with a choice of passing 

 from the first pool to the next and so on 

 up by swimming through the bottom 

 notches or jumping through the top 

 notches from one pool to the next higher 

 one. The jump in the latter case is not 

 more than eight inches and can be done 

 easily by almost any kind of fish. 



It is noted in the plan view of the 

 ladder shown in the accompanying 

 drawings that the notches in the bottom 

 of the cross partitions are placeil at the 

 lower end of the partitions to permit any 

 sediment to be washed out by the llow of 

 water. In the large drawing it is also to 

 be noted that the ladder is not placed in 

 close proximity to the spillway. The 

 reason for this is that fish in trying to 

 ascend a dam seek to pass up the largest 

 stream of running water. Due to the fact 

 that the \'olumeof running water issuing 

 from the ladder is usually less than that 



dropping over the spillway, the fish 

 would not find the ladder readily if it 

 were close to the spillway but would try 

 to swim up the spillway and would 

 probably dash themsehes to death 

 against the concrete buttresses. 



Borrowing the Night Lamps 

 of the Fireflies 



Just what the secret of the firefly's 

 light is the scientists have not as yet 

 discovered. Three necessary factors 

 have been found — water, oxygen and a 

 photogenic orlight-producing substance; 

 but a fourth is probably involved which 

 has thus far defied all research. The 

 children say it is the fairy lamplighter 

 whose wand lights the little lamps that 

 add so much to the beauty of a sum- 

 mer's night. However, a method has 

 been evohed of extracting and drying 

 the light-producing organs of the fireth' 

 without impairing the power of the 

 substance to phosphoresce. 



The dried material may be extracted 

 with water-free solvents. It is ground 

 up into a powder, and water containing 

 oxygen is atlded ; which gives the golden 

 glow without the assistance of either 

 the firefly's will or the fairy's wand. 



