WATERING, HEATING, VENTILATING AND SHADING 163 



THEORETICAL DISCHARGE OF 100 NOZZLES IN U. S. GALLONS 

 PER MINUTE 



The No. 1 outdoor nozzles and the No. 3 greenhouse nozzles are 

 the sizes most generally used 



, Head ^ , Type nozzles v 



Pounds Feet Greenhouse No. 2 Greenhouse No. 3 



5 11.55 11.5 176 



10 23.1 16.3 25.1 



15 34.7 19.9 30.8 



20 46.2 23.1 35.4 



25 57.8 25.8 38.6 



30 69.3 28.4 43.3 



35 80.9 30.6 46.9 



40 92.4 32.6 50.2 



The nozzle lines in the greenhouse may be supported 

 by special hangers provided for the purpose. Holes in 

 the pipe for the brass nozzles are made by a special drill- 

 ing machine. It is not a difficult matter to install an 

 overhead system of watering, and the manufacturers are 

 always pleased to give instructions on any point which 

 may not be fully understood. Whenever a pressure of 

 10 pounds or more can be obtained, it is possible to op- 

 erate the overhead system of watering, though a higher 

 pressure makes a finer spray. In fact, practical growers 

 prefer a pressure of not less than 25 pounds, and 40 

 pounds is better. 



Temperature. The proper temperatures for the various 

 greenhouse crops will be discussed in later chapters. It 

 should be said here, however, that a uniform tempera- 

 ture is important, unless sunshine should cause a wide 

 range in temperature, which will do no harm if free venti- 

 lation is given. An inadequate heating plant may be 

 responsible for low temperatures that are disastrous to 

 the crops. Ordinarily, excessively high temperatures 

 with poor ventilation do more harm than insufficient heat. 



Ventilation. The necessity of ventilation was dis- 

 cussed in Chapter VIII on Diseases and Their Control. 

 Every practical grower knows that plants in houses im- 



