Mr. H. Lamb on the Basis of Statics. 



187 



position of the source of light to the readings of all points on 

 the other loop, and the new readings will give the wave-lengths, 

 or multiples of them, for reflected light. The diffraction- 

 circle must be treated as two distinct loops, and the reading 

 of the source be subtracted from the readings on the circle for 

 transmitted, and added for reflected light. One of the zero- 

 readings occurs at the source of light, and the other at the 

 focus of ordinary reflected light. 



In the case of a plane grating, since c is infinite, the equa- 

 tion to the diffraction-curves becomes 



r = <icos 2 0. 

 Table showing the values of r for every five degrees of 6 in 

 the equation 

 cos 2 6 _ cos 1 

 r c d 



±9. 



H 



d=c. 



d=3c. 



H 



d=c. 



d-Zc. 



±0. 



90 



























90 



85 



2 



7 



18 



3 



8 



31 



95 



80 



9 



20 



77 



11 



37 



190 



100 



75 



21 



53 



113 



25 



90 



899 

 13691 



105 

 109 



70 



35 



87 



173 



44 



178 



-13451 



110 



65 



52 



126 



231 



73 



309 



- 2000 



115 



60 



71 



167 



300 



100 



500 



- 1500 



120 



55 



92 



209 



363 



140 



772 



- 1372 



125 



50 



113 



252 



423 



175 



1156 



- 1335 



130 



45 



135 



293 



481 



224 



1707 



- 1338 



135 



40 



156 



332 



535 



263 



2508 



- 1356 



140 



35 



176 



369 



582 



314 



3710 



- 1382 



145 



30 



194 



402 



625 



351 



5603 



- 1408 



150 



25 



210 



431 



663 



392 



8768 



- 1434 



155 



20 



224 



455 



694 



429 



14640 



- 1456 



160 



15 



235 



475 



718 



459 



27394 



- 1475 



165 



10 



243 



489 



736 



481 



63890 



- 1489 



170 



5 



248 



497 



746 



495 



261165 



- 1497 



175 







I 250 



500 



750 



500 



00 



- 1500 



180 



c=1000. 



XXIY. The Basis of Statics. By Hoeace Lamb, M.A., 



Professor of Mathematics in the University of Adelaide*. 



THE object of this paper is to suggest a new basis for the 

 science of Statics. The suggestion is put forward with 

 all diffidence ; but it will, I think, be readily granted that the 

 present form of the subject is hardly satisfactory. 



* Read at the Annual Meeting of the Association for the Improvement 

 of Geometrical Teaching, January 17th, 1883. Communicated by the 

 Association at the request of the Author. 



02 



