180 History of Luminescence 



The cause of all light was acid. In the case of the glowworm, an 

 acid emanation or exhalation {Ausdiinstung) appeared, and "one 

 can easily think that the SAveat pores must be incomprehensibly tiny 

 and delicate in such a small insect. The pores of [luminous] decom- 

 posing flesh [and fish] must be narrow also. In wood it is especially 

 oak-wood [which becomes luminous] where dampness makes the 

 canals through which the parts mix with the outer air, thin." Leh- 

 mann believed that " oak-wood contains ' Vitriol-Saure ' with a 

 metallic earth [iron] in so disintegrated [aufgeschlossenen] a form 

 that it must necessarily light." 



The green stone (fluorspar) of Saxony lights on heating because 

 it " contains a vitriolic acid salt which is decomposed by the warm- 

 ing and manifests itself as a true phosphorus." Lehmann devoted 

 several pages to preparation of phosphorus and also spoke of pyro- 

 phores. It is well known that chemically prepared phosphorus " con- 

 sist in great part of entirely disintegrated [volkommen aufge- 

 schlossenen] acid." The acid nature can be noted by the smell of 

 urine from which phosphorus is prepared. 



During the last half of the eighteenth century a number of tracts 

 appeared dealing with various types of luminescence, for example 

 the Dissertatio de Igne, etc. (1773) by Joseph Edler von Herbert 

 (1725-1794) , a Jesuit who became professor of experimental physics 

 at the University of Vienna and Canon of St. Stephan. Herbert 

 took the position that light and fire were the same thing and devoted 

 eighteen pages to the proposition: " Fire is liberated in the form 

 of light in phosphors and flame." 



The Phosphorescentia Adamantum, etc. (Viennae, 1777) by 

 Michaele de Grosser, A Series of Experiments Relating to Phos- 

 phori and the Prismatic Colours they are Found to Exhibit in the 

 Dark (London, 1777) by Benjamin Wilson (born 1708) and Delia 

 P'ietra Fosforica Bolognese (Bologna, 1780) by Camillo Galvani also 

 consider luminescences. All these contributions are discussed in 

 Chapter VIII on phosphorescence, since they deal entirely with this 

 field. 



No books or general contributions appeared in the latter part of 

 the century which can be regarded as general treatises on lumi- 

 nescence although papers on special luminous animals, on shining 

 wood and flesh, and burning of the sea were numerous. Two emi- 

 nent scientists, John Canton and Lazzaro Spallanzani, published 

 special papers. The writings of John Canton (1718-1772) include 

 the discovery of a bright new phosphor (Canton's phosphorus) in 

 1768, interesting observations on shining fish in relation to phos- 

 phorescence of the sea (1769) , and new observations on electro- 



