400 Mr. E. H. Cook on the Regenerative 



the field is to be produced. With the particular magnet we 

 have employed we see that ; at distances from the end of the 

 magnet very small compared with the length of the core, the 

 wire should all be coiled up at the near end of the core, as in 

 fig. 4 ; to create a field at a distance from the end of the mag- 

 net equal to about a third of the length of the magnet, it is 

 better to coil the wire uniformly over one half of the core, as 

 in fig. 2, than to cone it up at the near end as in 4 ; while 

 for distances from the end of the magnet equal to, or greater 

 than, about -§■ of the length of the core, the uniform mode of 

 winding is the best. 



We have to thank two of our students, Messrs. Sayers and 

 Pink, for most cordial assistance rendered us in this investi- 

 gation. 



LX. The Regenerative Theory of Solar Action, i?^ Ernest 

 H. Cook, B.Sg. (Lond.), A.R.C.S., Trade and Mining 

 School, Bristol*. 



I HA YE ventured thus to name the theory recently pro- 

 pounded by Dr. (now Sir Wm.) C. W. Siemens, in a paper 

 read before the Eoyal Society in March 1882, because of the 

 essential feature which it possesses. Solar heat is kept up, on 

 this theory, by supposing reciprocal actions to go on using only 

 the same materials but under different conditions. The diffe- 

 rent conditions are those which obtain in or near the sun and 

 those of interplanetary space — in the first case subjecting the 

 matter to intense heat and pressure, in the second to intense 

 cold and rarefaction. The theory has received considerable 

 discussion, more especially by MM. Faye and Hirn {Comptes 

 Rendus, Oct. 9 and Nov. 6, 1882) ; but there are some points 

 which, so far as I am aware, have not been raised. As the theory 

 possesses a very high scientific value, and as Dr. Siemens, in 

 enunciating it, states that he submits it " to the touchstone of 

 scientific criticism/' I venture to point out what appears one 

 or two difficulties connected with it. If another reason for 

 presenting these points for consideration be wanted, it is in 

 the hope that it will give Dr. Siemens the opportunity of 

 making some such interesting communication as he has done 

 in his reply to the criticism of M. Faye (Comptes Rendus, 

 Oct, 30, 1882)f. 



* Communicated by the Author. 



f The original paper and the whole of the published criticisms which 

 it has called forth, together with the replies of Dr. Siemens and other 

 matter, are contained in a volume recently published by Macmillan & Co., 

 entitled * The Conservation of Solar Energy.' 



