Dr. TyndalPs Remarks on the Researches o/Dr. Goodman. 127 



la the observations thus made, it is as far from being my wish, 

 as it is beyond my capability, to depreciate the labours of the 

 illustrious persons who have erected splendid specimens of art 

 on the foundations just described. They used these foundations 

 as they found them ; and if they be not sound and permanent, 

 we have only to lament that so much skill, ingenuity and indus- 

 try, were not bestowed on a more solid basis. 



11 Clare Street, Dublin. 



[To be continued.] 



XIX. Remarks on the Researches of Dr. Goodman " On the Iden- 

 tity of the Existences or Forces, Light, Heat, Electricity and 

 Magnetism." By Dr. Tyndall*. 



r I MIE December Number of the Philosophical Magazine con- 

 -*- tains an abstract of a paper bearing the above title, and 

 recently read before the Royal Society by its Secretary Mr. Bell. 

 Dr. Goodman finds, that on suspending a magnetized sewing- 

 needle within the helix of a galvanometer, and covering the in- 

 strument with a glass shade, when the sun is permitted to shine 

 strongly upon the instrument an electric current is developed in 

 the helix, which is indicated by its action upon the magnetized 

 needle. The direction of the current varies with the portion of 

 the instrument shone upon, and in some cases a permanent de- 

 flection of 10 or 12 degrees was obtained even ivhen the two ends 

 of the galvanometer wire were disunited. " During the course of 

 the experiments the circuit was established by means of a con- 

 necting wire between the mercury cups, and the circuit was again 

 and again completed, and as frequently broken, without any 

 deviation occurring in any of the results." -«Thc remarks made 

 farther on will, perhaps, excuse me to Dr. Goodman if I 

 propose the following modifications of his experiment : first, to 

 remove the magnetized sewing-needle and put an unmagnetized 

 one in its place ; secondly, to remove the steel needles altogether 

 and substitute in their stead one of copper or of wood; thirdly, 

 to remove the helix also, and leave the wooden or copper needle 

 and dial-plate alone within the shade. If, on submitting the 

 apparatus to the conditions described, in none of these proposed 

 cases an action epiite the same as that exhibited by the magnet- 

 ized needle can be observed, then is the discovery a most surpri- 

 sing one, and the momentous conclusion drawn from it in some 

 measure justified. I believe, however, that it has been the lot 

 oLmany cxpci ini< n tt ts to deal with phsenomena similar to those 



* Communicated by the Author. 



