412 APPENDIX. 



Marble. — A plate 25 X 25 X 2.5 cm., polished on both sides. It 

 can be re-polished after etching and used as often as desired. 



Filter pump. — Can be used if water service is available, or if a 

 head of 5 m. can be secured by tank. Korting's is excellent. 



Rulers. — 30 cm. long, graduated in millimeters. 



Brushes. — Camelhair brush of large size, and sablehair, smallest, 

 are useful. 



Pins. 



Tin tube. — 3 X 15 cm. See experiment 20. 



Absorbent cotton. — Also a roll of cotton batting. 



Sheet lead. — Light weight, used by plumbers. 



Plate glass. — Cut into pieces 20, 25, and 35 cm. square. 



Pine sawdust and clean sand. — For germinating seeds. 



