258 History of Luminescence 



j. j. dortous de mairan 



One of the most interesting early books, and the first compre- 

 hensive treatise devoted entirely to the aurora, was by Jean Jac- 

 ques Dortous de Mairan (1678-1771), entitled Traite Physique 

 de I'Aurore Boreale. The first edition, based on reports in the 

 Memoires of the French Academy (1731), appeared in 1733 and 

 recorded 229 displays of the aurora, dating from a. d. 502 until 1731. 

 The second edition (1754) recorded 2,137 displays gathered from 

 all records, although duplicate observations reduce the individual 

 number to 1,441. De Mairan must be credited with recognizing the 

 recurrent appearances of aurorae, as indicated in his memoires. 



The first edition of the Traite was reviewed in the Phil. Trans. 

 for 1734 by John Eames, who pointed out that most hypotheses pro- 

 posed by the learned 



suppose these Phosphorus like appearances to proceed from certain 

 Effluvia, either perspired out of our Earth, or at least passing through it. 

 But our ingenious Author has thought of a Cause very distant, as well 

 as very different from all these, viz., the Atmosphere of the Sun, which 

 at some time shows itself under the appearance of a Light, which he 

 calls the Zodiacal Light, but at other times produces an Aurora Borealis. 

 The Zodiacal light is the purer unmixed Atmosphere of the Sun: But 

 an Aurora Borealis is the effect of the Solar Atmosphere, consequent 

 upon its making a Descent into and blending itself with the Atmosphere 

 of our Earth, at certain Times and Seasons of the Year. . . . 



Attention had been called to the zodiacal light in the spring of 1683 

 by its discoverer, G. D. Cassini (1625-1712), who published an 

 account in the Journal des Sgavans, May 10, 1683. 



In the second edition (1754) , de Mairan answered those who had 

 disagreed with his hypothesis in a series of 21 " Eclaircissements." 

 He paid particular attention to the electrical theory which had be- 

 come popular since the first edition of his book (1733) but he took 

 a dim view of the theory, pointing out that electrical manifestations 

 (lightning) were known in the lower atmosphere but not in the 

 upper regions, and inquired how electricity could manifest itself a 

 whole night long in so different a form; why should electricity 

 appear so infrequently, even after years, to suddenly manifest itself 

 as an aurora; what is the relation of this material (electricity) to the 

 annual revolution of the earth that it should affect the frequency of 

 aurorae; by what mechanism or impulsion or attraction is the earth 

 inundated by electricity at the poles rather than in the torrid zone 

 where electricity is known to exist; finally how can one explain by 

 electric matter all the peculiar and varied manifestations of aurorae? 



