164 Prof. R. Bunsen on the Condensation of 



Table III. 



d. 



n. 



& 



w. 



d. 



n. 



d. 



n. 



d. 



n. 



d. 



n. 



1-2 



2 



3*5 



6 



4*7 



41 



5-9 



46 



7-1 



1 



8-5 



2 



20 



9 



3-6 



7 



4-8 



79 



6-0 



245 



7-2 



6 



8-7 



1 



22 



2 



3-7 



6 



49 



77 



6-1 



15 



73 



8 



8-8 



2 



2-3 



1 



3-8 



7 



50 



342 



62 



23 



7-4 



3 



9-0 



8 



25 



2 



39 



8 



5-1 



38 



6-3 



24 



75 



6 



92 



1 



2-6 



1 



4-0 



147 



52 



38 



6-4 



13 



7-6 



4 



9-4 



1 



27 



1 



4-1 



16 



5*3 



42 



6-5 



23 



7-7 



3 



9-8 



1 



2-8 



3 



42 



23 



54 



28 



66 



7 



7-8 



10 



9-9 



2 



3-0 



40 



4-3 



27 



55 



47 



6-7 



32 



7'9 



6 



10-0 



2 



3-2 



4 



44 



15 



5-6 



21 



6-8 



24 



8-0 



39 



10-8 



1 



3-3 



4 



4-5 



45 



5-7 



50 



6-9 



13 



8-2 



3 



11-0 



2 



3-4 



2 



4-6 



20 



5-8 



63 



7-0 



144 



8-3 



2 



12-0 



4 



If we take — 



Gr, the weight of the whole of the threads. in Table III., 



h 9 the length common to all, 



Q, the sum of their cross sections, 



dij the diameters of the, threads of a group measured in 



units of the micrometer-scale, 

 ft*, the number of threads in the group, and 

 s, the specific gravity of the threads ; 

 then 



G=sh±wa 2 2 i n.d*, .... (2) 



and 



Q=i7ra 2 2,Vf, (3) 



where the summation sign refers only to the particular group 

 treated of. The observations gave 



5 = 2-5056, a = 0*002945, 2.^ = 62415*4, 



where h is assumed =1000 millim. 



Then it follows from equation (2) that the 2000 threads in 

 Table III., taken at 1 metre long, weigh 1*0653 grm., and 

 that the sum of both end-surfaces of the whole 2000 only 

 amounts to 0*00000085032 square metre. Putting together 

 the foregoing data, we arrive at the following result. 



1877*4 threads of the spun glass, 1 metre long, go to a 

 gramme, which amounts altogether to 



a surface-area of 0*09450 square metres, 



a cross section of 0*0000007982 square metres, 



a volume of 0*39911 cubic centimetres. 



For a check on these results from the diameters of the threads, 

 five skeins were drawn from a stock of about 500 grms. of the 

 spun glass in different parts, cut to lengths of 2 metres, weighed; 



