NEW DOSAGE TABLES 7 



ten-foot tree received respectively four and sixteen ounces, a reduc- 

 tion of 25% would give 3 and 12, which have the same relation, that 

 is, one is four times the other. 2 and 12 might be nearer correct, which 

 would be in proportion of 1 to 6, intermediate between the 1 to 4 area 

 basis and the volume basis of 1 to 8. Likewise for a more leaky tent 

 a 25% increase, making 5 and 20 ounces, should more likely read 10 

 and 20. However, if the tables were constructed according to the 

 right system as regards the relation of size to dose a percentage increase 

 or decrease would result in the correct adjustment for different leak- 

 ages. The error in the calculation of the table is exactly of the same 

 character as that regarding size and leakage. 



Since the invention of the leakage meter we have a ready means 

 of learning just what the natural leakage of a tent is, and should 

 regulate our dose accordingly. Standing on the inside of the tent 

 one can see, between the interlacing of the fibres of the weave of the 

 cloth, hundreds of thousands of openings; though small enough to 

 prevent the passage of drops of water, they are very large compared 

 with the size of the gas particles which escape through these holes 

 without any hindrance. In dry weather the fibres shrink, leaving 

 larger openings which the meter will detect and measure, but to com- 

 pensate for which the dose should be larger. 



The diagram (Fig. 3) will show graphically the significance of 

 leakage. The average tent is equivalent to a tight tent with five rents 

 as large as the one here figured and many tents are operating with 

 a leakage as great as eight such openings and others as small as two. 

 One will make a fuss, and rightly so, if a fumigator uses a tent with a 

 number of acid burns big enough to put his fist through, but will very 

 complacently permit the use of a tent with a natural leakage ten times 

 as great. Natural leakage cannot be wholly prevented but should be 

 measured and compensated for by increased dosage and when this is 

 done tables properly calculated for dosage should, by all means, be 

 used. 



Where the Common Tables Are Right 



While the common tables are calculated on wrong principles it 

 should be remembered that the doses for average-sized trees of average 

 shape and for tents with average leakage, are correct and that serious 

 inaccuracies only occur when these average conditions are departed 

 from, and, furthermore, it may frequently happen that errors com- 

 pensate each other, where, as in this case, there are three different 

 kinds of errors varying independently of each other. The satisfactory 



