226 PICTURING MIRACLES 



be governed by the available air space, or in the 

 case of potatoes, the space available in the excelsior 

 in which they form. These lowly vegetables, given 

 space ten inches each way, have given at the rate of 

 two thousand bushels to the acre and at nine inches, 

 twenty-four hundred and sixty-five. A tank with an 

 excelsior layer ten inches thick, allowing the pota- 

 toes ample vertical space for growth. Planted four or 

 five inches apart, produced at the rate of about four 

 thousand bushels to the acre; but such crowding, 

 curtailing both sun and air, is not advisable in large 

 tanks. 



For my own experimental and photographic work, 

 I made wooden tanks about four feet long by one 

 foot wide, with a depth of six inches. In these, I 

 placed wire baskets, like those you might use on 

 your desk, for letters, fitted into the tank's space. 

 These I filled with excelsior, and being portable, 

 enabled me to take the baskets out and examine the 

 plant's roots. Sometimes I put them in a smaller con- 

 tainer to pose before a lapse-time camera for re- 

 cording growth, or put them in our living room, 

 giving living, growing, instead of cut flowers. 



While this method has many advantages for my 

 work, it is not suitable for potatoes, or similar crops, 

 not giving them sufficient space; also I found in 

 these tanks that the water level is more difficult to 



