378 
Rev. Mr. Powell’s experiments relative to 
2 Reflectors, 12 inches distant. No. II. 
1st Screen 2 in. — 2nd 3J in. from ball. 
No Screen, 
1 Screen, 
2 Screens. 
Min. 
Sec, 
Focal 
Fecal 
Temp, of 
Focal 
Temp, of 
Temp, of 
Therm. 
Therm. 
Screen. 
Therm. 
1st Screen. 
2d Screen. 
0 
MM 
17 
17 
18 
>7 
>7 
>7 
3° 
21 
17.25 
20.5 
*7 
19.5 
>7 
1 
— 
24 
1 7-75 
25 
17.25 
25.5 
>7-5 
3 ° 
26 
18 
27 
>7-5 
3° 
18 
2 
— 
28 
18.5 
30 
>75 
33 
18.5 
3° 
29.5 
18.75 
32.5 
>7-5 
35 
18.5 
3 
— 
3°-5 
19 
34 
17.5 
37 
19 
3° 
3 1 
19.25 
35 
>7-5 
38 
19.5 
4 
■ — 
3>-5 
*9-5 
3 6 
>775 
39-5 
20 
30 
3>-5 
>9 75 
37 
>7 75 
40 
20 
5 
3>-5 
>9-75 
37-5 
>775 
40.5 
20 
3° 
3>-5 
>9-75 
37-5 
>775 
405 
20.5 
6 
— 
31-25 
>975 
38 
>7-75 
4°-5 
20.5 
3° 
3 I - Z 5 
1 9 75 
38 
>7-75 
40.5 
21 
7 
— 
3 1 
>9-75 
38 
>7-75 
40 
21 
3° 
>9-75 
37-5 
>775 
40 
21 
8 
— 
19.75 
37-5 
17-75 
39 
21 
3° 
>9 75 
37 
1 3 
39 
21 
9 
— 
>9 75 
3^5 
18 
38.5 
21 
30 
>9-75 
3 6 
18 
38 
21 
10 
* 
>9-75 
35-5 
>7-75 
37-5 
21 
3° 
>9-75 
35 
>7-75 
37 
21 
11 
— 
19.5 
35 
>7-75 
37 
21 
30 
19 5 
34-5 
>775 
3 6 -5 
21 
12 
— 
19-5 
34 
>775 
3 6 
21 
3° 
19.5 
33-5 
>775 
35-5 
21 
>3 
— 
19.25 
33 
>775 
35 
21 
30 
19.25 
33 
>775 
34-5 
21 
14 
— 
19.25 
32-5 
17-75 
34 
21 
30 
>775 
33-5 
21 
>5 
"" 
>775 
3 
21 
9.) From these results ( with which all the others I obtained 
closely agree) I conceive it fully appears,— 
1st. That the additional diminution occasioned by the second 
