314 MM. Struve and Dollen on the Correction 



which have not an interest when that is the case. To those 

 who are already cognizant of the issue, the arguments advanced 

 by the authors on both sides cannot but have a stronger in- 

 terest, especially if they have never seen, or have forgotten, 

 the original ; for that matter, I may say that I myself did not 

 know of it, and have never seen an allusion to it in English 

 literature. 



I must not conclude this brief introduction without apology 

 alike to authors and readers for the inelegance of the trans- 

 lation. A thankless task at best, translation becomes trying 

 in the extreme when, as in this case, it is done first by a 

 writer unacquainted with the technicalities of the subject, and 

 afterwards revised. As I have dealt freely with the first 

 e'bauche in the earlier pages, and discarded it entirely in the 

 later, I must take the whole responsibility, and will hope that 

 at least some of the many blemishes will be forgiven. 

 I remain, gentlemen, 



Very respectfully yours, 

 Colliiigwood, Feb. 1, 1881. J. HeeSCHEL. 



On the 4th of May of the past year [1860] a paper by 

 General Schubert was laid before the physico-mathematical 

 class by the perpetual secretary, in which it was proposed, in 

 reference to an essay published in the Astronomisclie 

 Nachrichten, no. 1245, " Sur l'influence des attractions locales 

 dans les operations geodesiques," that the Academy should 

 undertake careful levelling in the vicinity of all, or at the 

 least of some specially selected stations of the great Russo- 

 Scandinavian Arc. According to General Schubert, these 

 levels are necessary to bring the arc up to the present state of 

 our knowledge, as without them it should, not be considered 

 complete. 



At that time I had already started upon my journey to 

 Spain for the purpose of there observing the eclipse of the 

 sun. The Academy committed to Herr von Dollen, my repre- 

 sentative for the time at the Observatory, the task of reporting 

 upon General Schubert's proposal. Herr Dollen fulfilled the 

 commission by an essay which was laid before the Class at its 

 next sitting, on the 18th of May. His clear and lucidly ex- 

 pressed opinion proved to be almost throughout diametrically 

 opposed to that of General Schubert, summing up the matter 

 thus : — That he (Dollen) assented in no way, either to General 

 Schubert's arguments, or to the proposals founded upon them. 

 On account of the importance of the subject, and especially in 

 consideration of the distinguished proposer of the scheme, who 



