Prof. TyndalPs Notes on Scientific Histonj. 49 



to have been wronged, have, before his intervention, been fully- 

 ventilated, discussed, and settled by the general award of 

 scientific men." Such rashness is rare in a man occupying so 

 responsible a position. The fact really is that if it could be 

 shown that Prof. Thomson had, " before my intervention," been 

 aware of what Mayer had done, he would at the present moment 

 be in as unenviable a position as could possibly be occupied by 

 a scientific man. I may add that he has never yet rendered to 

 Dr. Mayer the credit which belongs to him. 



58. How far Mr. Joule's lecture on shooting-stars (23) affects 

 the essay of Dr. Mayer on Cosmical Dynamics the reader must 

 himself determine. Here is the extract from the f Manchester 

 Courier ' (12th May 1847) referred to by Mr. Joule and printed 

 in the Philosophical Magazine. " You have no doubt frequently 

 observed what are called shooting -stars, as they appear to emerge 

 from the dark sky at night, pursue a short and rapid course, 

 burst, and are dissipated in shining fragments. From the 

 velocity with which these bodies travel there can be little doubt 

 that they are small planets, which in the course of their revo- 

 lution round the sun are attracted and drawn to the earth. 

 Reflect for a moment on the consequences which would ensue 

 if a hard meteoric stone were to strike the room in which you 

 are assembled with a velocity sixty times as great as a cannon- 

 ball. The dire effects of such a collision are effectually prevented 

 by the atmosphere surrounding our globe, by which the velocity 

 of the meteoric stone is checked, and its living force converted 

 into heat, which at last becomes so intense as to melt the body 

 and dissipate it in fragments, too small probably to be noticed in 

 their fall to the ground. Hence it is that, though multitudes 

 of shooting-stars appear every night, few meteoric stones have 

 been found, those few corroborating the truth of our hypothesis 

 by the marks of intense heat they bear on their surfaces." 

 Those who have read Mayer's essay will never forget it, and will 

 be able to judge how far its character could be affected by the 

 above extract ; even had it been under the eyes of Mayer from the 

 moment of its publication. Those who have not read Mayer, 

 will find him translated in the Phil. Mag. vol. xxv. pp. 241, 387, 

 417. In my book on Heat I have given Mr. Joule due credit 

 for the above hypothesis*. 



59. More than a year ago I addressed a letter to Prof. W.Thom- 

 son which gave me great pain to write. I wrote it partly in de- 

 fence of Dr. Mayer, partly in defence of my own character. It was, 

 I am told, vigorously expressed, but it has never been intimated 



* The hypothesis of the cosmical origin of meteorolites is due to 

 Chladni, the protective power of the atmosphere and its sufficiency to dis- 

 sipate meteors being the point brought forward by Mr. Joule. 



Phil. Mag, S. 4. Vol, 28. No. 186. July 1864. E 



