1919.] New Zealand Institute Science Congress. 305 
Megger and Fifty-cycle-pressure Tests on Three Old Stock X Insulators 
for the 66,000-volt Line. 
No. of 
Insulator. 
First Shell. 
Second Shell. 
Third Shell. 
Fourth Shell. 
Crown to Pin. 
Meg. 
50-eye. 
Meg. 
50-cyc. 
Meg. 
50 eye. 
Meg. 
50-cyc. 
Meg. 
50-cyc. 
347 S .. 
o • 
0 
150 
45 KV 
30 
40 KV 
70 
50 KV 
250 
100 KV 
Failed. 
Failed. 
O.K. 
O.K. 
808 B .. 
0 
0 
40 
30 KV 
500 
50 KV 
60 
50 KV 
600 
100 KV 
Failed. 
O.K. 
O.K. 
O.K. 
258 S .. 
0 
0 
80 
50 KV 
100 
50 KV 
30 
50 KV 
600 
100 KV 
O.K. 
O.K. 
O.K. 
O.K. 
By “ 0 ” is meant too low to be recorded on the voltmeter, and by “ O.K. ” that 
the shell stood up to the test. 
Preliminary experiments (not recorded here) had shown that insulators 
showing the fracture appearance that these did could be made to absorb 
colouring-matter, and it was therefore decided to make the test more 
severe by increasing the time during which the specimens were under 
pressure, with a view to seeing into the character of the penetration. They 
were therefore subjected to sixty-nine hours’ average pressure of 2,0001b. 
per square inch. The samples were all from insulators of X make. 
Specimen. 
Weight dry. 
Density 
Increase in 
Weight. 
Grammes. 
Grammes. 
A .. 
.. 87-107 
2-320 
•436 
B .. 
.. 86-534 
2-342 
•462 
C .. 
.. 77-066 
2-338 
•719 
D .. 
.. 62-383 
2-338 
•352 
E .. 
.. 78-891 
2-350 
•242 
F .. 
.. 56-142 
2-329 
•436 
G .. 
.. 46-019 
2-324 
•546 
H .. 
.. 64-585 
2-253 
•202 
I 
.. 36-373 
2-354 
•007 
J .. 
.. 25-914 
2-364 
•024 
Specimen A was a totally unglazed piece from the crown of the second 
shell of insulator 258 S ; specimen B was a partly glazed piece of insulator 
808 B — second shell near but not on the crown ; C was from the “ neck ” 
of the first shell of insulator 347 S, partly glazed (about an inch from 
where it was taken there was visible the track where the spark had passed in 
the fifty-cycle-pressure test) ; D, unglazed piece from crown of second shell 
of insulator 258 S ; E, totally unglazed portion from third shell of insulator 
347 S ; F, almost completely glazed part of 808 B ; G-, piece of 808 B 
completely glazed on both sides ; H, quite unglazed piece from near the 
crown of the second shell of 347 S ; I, beak-shaped piece embracing part 
of the crown of third shell of 258 B, quite unglazed ; J, small piece, 
partially glazed, of third shell of insulator 258 B, from near the neck of 
that shell. 
It seems hardly necessary to point out that such an expression as 
“ completely glazed ” used above refers only to the faces exposed in 
the manufacture of the shell. In the preparation of the specimen in 
23—Science. *■ 
