132 Mr. Loyd A. Jones on a Method and Instrument 



has been obtained ; the greater part of this refers to the visi- 

 bility of small boat models camouflaged in various ways. As 

 was previously stated, it is not the object of this paper to 

 present the results of this work. However, in order to 

 convey a more definite idea of the performance of the 

 visibility meter a single set of data and one pair of curves 

 will be included. In Table I., under the heading F 20, are 



Table I. 

 F20. Eo = -43. 



w. 



V. 



W. 



V. 



•40 



1-5 + 



•10 



81-5 + 



•47 



2-5- 



•20 



27-8+ 



•70 



10-0- 



•25 



17-0+ 



•90 



11-5- 



•30 



9-9 + 



-.30 



12-5+ 



•35 



4-6+ 



•34 



5-0+ 



•40 



0-9 + 



•25 



2-5 + 



•414 



o-o 



•42 



2-5 + 



+o 



o-o 



•38 



4-0 + 



•447 



0-0 



•55 



5-5- 



•50 



2-6- 



•42 



0-9 + 



•60 



6-3- 



•45 



1-0- 



•70 



9-0- 



•78 



9-0- 



•80 



11-0- 



•35 



8-5+ 



•90 



12-6- 



•50 



3-0- 



1-00 



13-8- 



given the visibility values, V, for various weather coefficients,, 

 W. The model used was painted a flat bluish-green gray and 

 was of the lowest average visibility for the period covered 

 by the observations. The specifications of colour and 

 reflecting power for this model are : 



Reflexion Factor *43 



Wave-Length of Dominant Hue ... 488 /jl/ll 

 Saturation 88 p. c. white. 



Many more observations than are given in Table I. were 

 made but those presented are considered as typical and cover 

 the maximum range of W values encountered. In the 

 columns under the heading B<, = *43 are the theoretical values 

 of V corresponding to a series of assumed values for W, and 

 lv 2 — -43. The observed and computed values are plotted in 

 fig. 13. The fact that the minimum visibility of the model 

 F 20 was practically zero shows that the hue contrast, C Jn and 

 saturation contrast, C s , between model and background must 



