THERMO-ELECTRIC DIAGRAM FROM -200° C. TO 100° C. 



777 



fig. 19 is reproduced in facsimile from the original curve. The curve was tested, as 

 in other cases, by marking the mid-points of a series of parallel chords, all of which 

 mid-points are shown on the diagram. Thus the straight line marked A was found 

 from the seven mid-points, a lt . . . a. Through a-y a short line is drawn which is a 

 portion of the first chord, whose mid-point is a x ; all the other chords of this series are 

 parallel to it. From the diagram the points given in Table XIII. were read off, and by 

 means of them the best line through them was calculated by least squares. This is 

 the A-line shown in the diagram. The first two series of mid-points plotted were those 

 of B and C. The departure from parallelism of these two sets of points was too marked 

 to leave any idea of the curve being a parabola. Consequently, other sets of mid-points, 

 six altogether, were plotted, A, B, . . . F, whose co-ordinates were read off and entered 

 in Table XIII. For each of these series of points the equation of the corresponding- 

 straight line was calculated by least squares, with the following results : — 



Table XIII. 



Table of Mid- Points of Parallel Chords. 

 The Top Line gives the Inclination of the Chords. 



A, tan 



l (-i> 



B, tan- 1 0. 



C, tan l \. 



D, tan" 1 1. 



E, tan- 1 f . 



F, tan" 1 2. 





E 





E 





E 





E 





E 





E 



*. 



100' 



*. 



100' 



t. 



100" 



*. 



100' 



*. 

 + 4°-0 



100' 



*. 



100' 



- 77-7 



1013 



- 58-5 



150- 



- 45°-5 



227-5 



- 15-5 



184-0 



176-3 



+ 19°-5 



163-5 



-73-0 



86-5 



-52-5 



i25- 



-41-5 



204-0 



- 13-0 



162-0 



5-0 



156-0 



210 



141-5 



-690 



72-5 



-47-5 



100- 



- 38 



181-0 



-10-5 



139 



6-5 



134-5 



225 



120-0 



-640 



57-0 



- 42-0 



75- 



-33-5 



157-5 



- 7-5 



116-5 



8-0 



112-5 



23-5 



98-0 



-60-0 



44-5 



-37-0 



50- 



- 30-0 



135-0 



- 5-0 



94-0 



10-5 



91-5 



25-5 



75-5 



-55-5 



27-5 



-33-0 



25- 



-26-0 



112-0 



- 30 



72-3 



12-7 



68-5 



26-3 



535 



-51 3 



13-5 



-28-0 



o- 



- 23-0 



88-5 



- 0-5 



490 



14-0 



46-0 



27 



43-7 











-19-5 



66-0 



+ 1-3 



26-0 



14-5 



22-0 















-160 



42*0 



+ 3-3 



5-0 



















-140 



18-0 















... 









-10-5 



-5-5 















For A, 



„ B, 



„ c, 



„ D, 



„ E, 



„ F, 



j--+ 3-3098*= -155-468^ 



+ 4-9519*= -136-164 



100 



^+ 6-5908*= - 66-796 



~q+ 9-4176*= + 41-464 

 ™ + 12-9969* = +223-083 



100 



+ 15-9485*= +475-998/ 



• (76) 



TRANS. ROY. SOC. EDIN., VOL. XLVII. PART IV. (NO. 25). 



114 



