Ohservations of the Transit of Mercury, 191 



were occasionally transient mottlings of the disc; but 

 these I attribute to persistence of vision, since thej did 

 not appear to my eye except when the telescope was vibrated 

 by occasional gusts of wind. Several visitors who were 

 with me during the afternoon viewed the planet as shown 

 in the telescope with the same result. 



In conclusion I present a summary of the Dudley Ob- 

 servatofy observations of contact in Albany local mean- 

 time. 



Contacts. 



Observer. I. n. m. IV. 



Boss, 22h 20"™ 49.^0 



Landreth, 22i> 50.^0 29.5 S'^ 47'" 20.^7 5'' 49"^ 53.^2 



Wilson, [18 17.5] 42.0 04.2 52.2 



The details relating to the observations at the Helder- 

 berg station follow in Mr. Landreth's own words. 



REPORT OF MR. 0. H. LAITDRETH. 



Dudley Observatory, May 28, 1878. 



*Dear Sir: 



In accordance with your request, I beg leave to submit 

 the following report, relating to observations made by the 

 party dispatched from the Dudley Observatory, to observe 

 the transit of Mercury on May 5-6, 1878. 



In considering the probability of the 6th of May being 

 favorable for observation it was deemed advisable by you 

 that entire dependence should not be placed on the chances 

 of the occurrence of favorable weather at Dudley Observa- 

 tory, but that a party be sent, with the necessary equip- 

 ments, to some point differing in atmospheric conditions 

 from Albany. Accordingly, after consultation with Pro- 

 fessor Gardner and Mr. Wilson of the N. Y. State Survey, 



