DUNN'S OBSERVATIONS OP INGRESS. 243 



All the times recorded refer to the internal contact at Ingress. I observed 

 the external contact, but not, I think, with sufficient accuracy to allow me to 

 record it. Moreover, I did not like to take the time of external contact, lest 

 I should be biassed by the calculated interval between the external and 

 internal contacts. 



There was scarcely any appreciable " boiling " of the Sun's limb. 



The observing telescope was mounted on a solid wooden post within the 

 inclosure, but sufficiently far from the fence to prevent the heated air 

 streaming from the top of the fence producing, by its changeable refraction, 

 any unsteadiness in the view. The power used was a Hughenian eye-piece 

 of 130. 



R. JOHNSON. 



The telescope used by Mr. Johnson was an achromatic by Dollond of 

 3|- inches aperture and 46 inches focal length, of excellent definition. It was 

 fitted by Messrs. Troughton and Simms with a solar diagonal reflector. Dark 

 glasses screwed on at the eye-end. It had a steady but simple kind of 

 equatorial mounting, attached to the top of a heavy baulk of timber sunk 

 several feet in the ground, and was used in the open air. There was a slow- 

 motion screw in Right Ascension with a convenient handle. 



MR. R. DUNN'S OBSERVATION. 



The Reverend Robert Dunn, of Honolulu, having expressed his intention 

 of visiting Waimea about the epoch of the Transit of Venus, there was placed 

 at his service an achromatic by Dollond, belonging to the Royal Observatory, 

 Greenwich, of 2'7 inches aperture and 33 inches focal length, fitted with a 

 solar diagonal reflector, negative eye-pieces of powers 67 and 134, and a 

 neutral tint achromatised wedge. The telescope was mounted upon a firm 

 tripod stand, with altazimuth movements and steadying rods of the usual 

 construction ; but, in consequence of the shortness of the tube between the 

 eye-end and the principal point of support, and the absence of mechanism 

 for giving slow motion, it was difficult to follow the diurnal motion, especially 

 with the higher power. 



Mr. Dunn practised for several days with the model at Honolulu. Such 

 observations could be made with this small instrument quite as accurately as 

 with the larger ones, with the power 134, but not with the lower power. 



i i 



