Ridge Counting

The number of ridges intervening between the delta and the core is

known as the ridge count. The technical employees of the Federal

Bureau of Investigation count each ridge which crosses or touches an

imaginary line drawn from the delta to the core. Neither delta nor

core is counted. A red line upon the reticule of the fingerprint glass

is used to insure absolute accuracy. In the event there is a

bifurcation of a ridge exactly at the point where the imaginary line

would be drawn, two ridges are counted. Where the line crosses an

island, both sides are counted. Fragments and dots are counted as

ridges only if they appear to be as thick and heavy as the other

ridges in the immediate pattern. Variations in inking and pressure

must, of course, be considered.



Figures 72 to 97 and figures 98 to 101 show various loop patterns. The

reader should examine each one carefully in order to study the cores

and deltas and to verify the count which has been placed below each

pattern.





[Illustration: 72. 12 counts.]



[Illustration: 73. 2 counts.]



[Illustration: 74. 16 counts.]



[Illustration: 75. 7 counts.]



[Illustration: 76. 4 counts.]



[Illustration: 77. 7 counts.]







[Illustration: 78. 15 counts.]



[Illustration: 79. 16 counts.]



[Illustration: 80. 9 counts.]



[Illustration: 81. 3 counts.]



[Illustration: 82. 9 counts.]



[Illustration: 83. 20 counts.]







[Illustration: 84. 6 counts.]



[Illustration: 85. 2 counts.]



[Illustration: 86. 8 counts.]



[Illustration: 87. 14 counts.]



[Illustration: 88. 5 counts.]



[Illustration: 89. 12 counts.]







[Illustration: 90. 12 counts.]



[Illustration: 91. 3 counts.]



[Illustration: 92. 16 counts.]



[Illustration: 93. 14 counts.]



[Illustration: 94. 16 counts.]



[Illustration: 95. 18 counts.]







[Illustration: 96. 2 counts.]



[Illustration: 97. 1 count.]



[Illustration: 98. 1 count.]



[Illustration: 99. 2 counts.]



[Illustration: 100. 8 counts.]



[Illustration: 101. 13 counts.]



Figure 102 is a sketch reflecting the various types of ridges which

the classifier will encounter when engaging in counting loop patterns.



In figure 103, the lighter lines are caused by the splitting or

fraying of the ridges. Sometimes ingrained dirt will cause a similar

condition between the ridges. These lines are not considered ridges

and should not be counted.



In figure 104, the dot is not the delta because it is not as thick and

heavy as the other ridges and might not be present if the finger were

not perfectly inked and printed.



When the core is located on a spike which touches the inside of the

innermost recurving ridge, the recurve is included in the ridge count

only when the delta is located below a line drawn at right angles to

the spike.



Figures 105 and 106 are examples of this rule.



If the delta is located in areas A, the recurving ridge is counted.



If the delta is located in areas B, the recurving ridge is not

counted.







LOOP

25 RIDGE COUNTS



1. SHORT RIDGE

2. }

3. } BIFURCATION

4. }

5. } BIFURCATION

6. RIDGE

7. ENDING RIDGE

8. }

9. } BIFURCATION

10. RIDGE

11. ENDING RIDGE

12. RIDGE

13. SHORT RIDGE

14. }

15. } BIFURCATION

16. }

17. } ISLAND

18. }

19. } BIFURCATION

20. ENDING RIDGE

21. DOT

22. RIDGE

23. }

24. } ISLAND

25. ENDING RIDGE