624 BUNSEN MEMORIAL LECTURE. 



During- my absence from Heidelberg in the Christmas holidays a man 

 employed there in cutting wood, in spite of previous warnings, inex- 

 cusably took his little son with him into the laboratory and allowed 

 him to run about without proper supervision. The child seems to 

 have put into his mouth an iron tube which had been used for the 

 reduction of metallic rubidium ])y heating the carbonate wdth charcoal, 

 and in which the explosive compound carbonic oxide-rubidium had 

 been formed. The result was that an explosion occurred, and although 

 no mechanical wounding took place the child's throat and roof of its 

 mouth were fearfully l)urned, so nuich so that it died within twelve 

 hours. You can imagine how much I have been ati'ected by this acci- 

 dent, although, heaven be thanked, no blame for want of caution can 

 be attributed to me." 



In 1875 (Pogg. Ann., 1875 (155), 230,366) Bunsen published a long 

 investigation upon the spark spectra of the rare earths. He had con- 

 structed, and describes there, a new and convenient form of carbon- 

 zinc chromic acid battery which was suthcientl}' powerful to give a 

 small arc light or to work a large induction coil, and could be put in 

 and out of action, so that it was made ready for instant use by lower- 

 ing the carbons into the exciting liquid. B}' the help of this battery 

 Bunsen mapped the spark spectra of the rare earths, the separation of 

 which has proved to be a tedious and very lal)orious piece of work. 

 An accident, almost pathetic in its incidents and somewhat similar 

 to the well-known accident which happened to Newton's manuscript, 

 occurred to Bunsen. He had just completed the above-named 

 research, and the tinished manuscript lay upon his writing table. On 

 his return from dinner one day he found the whole reduced to ashes. 

 It seems that a spherical water bottle stood on his desk, and this, act- 

 ing as a lens in the sunlight, was the cause of the disaster. Writing 

 to me on June 3, 1874, he says: 



"You have good cause to be very angry with me for not having 

 answered your sympathetic letter before this; but I have not allowed 

 mvself lately to think of anything which would remind me of the loss 

 of my burned research. '" ■■' * I had finished the editing of a memoir 

 on a subject which had occupied me for three years, and was about to 

 forward it to Poggendorff for publication, when on returning home 

 the other day I found all these papers, which had caught lire during 

 my al)sence. reduced to ashes. The photogi'aphs of th(^ apparatus, the 

 drawings of the spark spectra of the metals of the rare earths, to 

 separate and map which had cost me untold trouble, all are burned." 



With regard to this accident, Kirchhoff writes to me on May 22: 



"The disaster of which you read in the papers really happened. 

 The manuscript of a research at which he had labored for years, with 

 maps of spectra, has been burned. He was, to begin with, much 

 depressed, but his wonderful elasticity of mind enabled him to over- 

 come his dejection, and he has alreadj^ begun to replace what was lost." 



This he continued to do, never drawing rein until the memoir was 

 again ready for press. 



