OFFICIAL EMPLOYMENT. 149 



of the stratifications run from south to east. I have been 

 for three years collecting observations for this work, and it 

 is not from laziness, but from a wish to produce something 

 really valuable, that it has been kept so long from the public.' 



In a similar strain he writes to the minister Von Heinitz on 

 February 3, 1796 : ' I have succeeded in arranging a general 

 system for the inclination of the strata with respect to the 

 horizon, as well as for the order in which the strata are super- 

 posed. It is a very remarkable phenomenon, which has hitherto 

 escaped the observation of our physicists. My work will be 

 published in the course of the summer, and I shall consider 

 myself well repaid for the many journeys I have undertaken on 

 foot, and the fatigue I have undergone, if this endeavour to 

 establish the laws of geology should be deemed worthy of the 

 support of your Excellency.' . . . 



This work, however, was never published ; the information 

 collected for it was incorporated into a later work, entitled, 

 c Essai geognostique sur le Gisement des Eoches dans les deux 

 Hemispheres.' 



The second work on which he was engaged was 'Experi- 

 ments on the Excitability of the Fibres of the Muscles and 

 Nerves, with Conjectures on the Chemical Process of Life in the 

 Animal and Vegetable Kingdoms.' As early as 1792, during 

 his first visit to Vienna, Humboldt became acquainted with the 

 discoveries of Gralvani and Volta ; l from that time he watched 

 the discussions of physicists as to the nature and cause of 

 animal electricity, and undertook repeated experiments and 

 counter-experiments, not confining himself merely to the frog 

 hitherto the favourite subject of all such investigations but ex- 

 perimenting upon his own person, with an amount of self-sacri- 

 fice so^extreme as to produce a permanent derangement of the 

 nervous system. Detailed accounts of the experiments he in- 

 stitutedyand records of the progress of his work, are contained in 

 numerous letters, both published and unpublished, to Blumen- ] 

 bach, 2 Sommering, Herz, Eeil, Grirtaner, Willdenow, Marc- Aug. 



1 t Versuche liber die gereizte Muskel- und Nervenfaser, nebst Vermu- 

 thungen iiber den Chemischen Process des Lebens in der Thier- und 

 Pflanzemvelt.' Preface, p. 3. 



2 ' Blumenbach,' writes Humboldt to Freiesleben, f may possibly add 



