Overstrain  and  Recovery  of  Aluminium,  etc.  385 
A  third  overstrain  and  similar  series  of  tests  were  made 
starting  28  days  after  the  first  overstrain,  with  the  result 
shown  in  Table  III. 
Table  III. — Specimen  No.  9  (Third  Overstrain] 
1st  Loading, 
2nd  Loading. 
3rd  Loading. 
4th  Loading. 
Time 
Load 
Dec.  8, 
1904. 
20  nits,  after 
1  hour  after 
5  days  after 
overstrain . 
overstrain. 
overstrain. 
in 
in 
IVlinutes. 
Tons. 
Reading. 
Diff. 
Reading. 
Diff. 
Reading.    Diff. 
Reading. 
Diff. 
0 
0 
200 
200 
200 
200 
1 
0-5 
235 
35 
239 
39 
238          38 
237 
37 
2 
1-0 
•272 
37 
278 
39 
277 
39 
274 
37 
3 
1-5 
308 
36 
316 
38 
314 
37 
312 
38 
4 
20 
343 
35 
356 
40 
354 
40 
349 
37 
5 
2-5 
380 
37 
396 
40 
393 
39 
387 
38 
6 
3-0 
416 
30 
437 
41 
434 
41 
426 
39 
7 
3-5 
452 
36 
479 
42 
475 
41 
466 
40 
8 
4-0 
490 
38 
524 
45 
517 
42 
506 
40 
9 
4-5 
529 
39 
567 
43 
559 
42 
546 
40 
10 
5-0 
570 
41 
611 
44 
603 
44 
587 
41 
11 
5-5 
610 
40 
656 
45 
646 
43 
630 
43 
12 
60 
651 
41 
13 
6'5 
696 
45 
14 
70 
742 
46 
15 
7-5 
790 
48 
16 
8-0 
842 
52 
17 
8-5 
902 
60 
19 
110 
Specimen  No.  8  was  cut  from  the  same  bar  as  No.  9,  and 
was  tested  in  exactly  the  same  way  and  at  the  same  intervals 
as  No.  9,  except  that  between  the  first  and  second  and  between 
the  second  and  third  loadings  in  each  series  the  specimen  was 
subjected  to  a  temperature  of  99°  C.  for  3  minutes  by  means 
of  a  water-bath,  and  then  cooled  to  the  temperature  of  the 
atmosphere.  The  results  of  the  three  series  of  tests  are  given 
in  Tables  IV.,  V.,  and  VI. 
Fig.  2  shows  the  load-extension  curve  for  the  first  over- 
strain of  specimen  No.  8  (A),  and  the  three  subsequent  tests 
B,  C,  and  D  in  respective  order.  That  the  recovery  due  to 
the  heating  is  much  quicker  than  for  specimen  9  is  obvious 
from  a  comparison  of  figs.  1  and  2. 
Figs.  3,  4,  and  5  also  exhibit  the  quicker  recovery  under 
the  influence  of  heat  for  the  three  overstrains  at  such  in- 
tervals that  recovery  from  one  was  practically  complete  before 
the  next  took  place.  The  full  lines  represent  the  behaviour 
of  specimen  No.  9  recovering  without  heat  (see  Tables  I.,  II., 
