Notes and Memoranda. 79 



NOTES AND MEMORANDA. 



Food of the Heron. — T. Y. Greet, Esq., of Morris Hall (near Edinburgh), 

 writes ; " On the 7th instant my keeper shot a young heron. To-day, on being 

 prepared for table, it was found to contain two redwing thrushes and a water- 

 wagtail ; one of the former was in a most perfect condition, hardly a feather 

 removed. Is such a thing usual in the heron's habit of feeding?" [In Morris's 

 British Birds the herou is described as omnivorous, and, amongst other things, 

 is said to eat the young of other birds. Ed.] 



Gauging the* Light of Spots on the Moon, and Checking Additions. — 

 The Rev. N. J. Heineken writes : " It has occurred to me, in connection with the 

 supposed altered brilliancy of the spot ' Linne ' in the moon, that it might from 

 time to time be tested by comparison with some other fixed place in the moon. 

 This might possibly be done by a shade of thin metal over a portion of the dia- 

 phragm of the eye-piece, which shade should be pierced with a very fine hole, the 

 light admitted through which could be at any period reduced to the same intensity 

 as that exhibited by the spot under examination, by shades, or a wedge of ground 

 glass, or other means. The comparison could thus be always made with one test 

 spot. The plan in fact is not uulike the lamp micrometer of the elder HerscheL 

 In a former letter I mentioned to you the application of Perkins's pedometer to 

 the counting of meteors, and I have lately found it very useful as a check upon 

 the tedious and often uncertain process of addition. For instance, in ascertaining 

 the result of metorological observations, the string is pulled for each unit in a 

 column, the tens carried to the next, the same written down and divided by the 

 days as usual to obtain the means. This I have found a complete check upon 

 previous ordinary addition. If the above suggestions appear of any value, pray 

 make use of them as you think fit. The plan proposed for observations on the 

 moon I have lately tried myself with a prospect of success." 



Me. Rutherford's Celestial Photography. — Dr. Gould, writing in 

 Astronomische JStachritfiteii, states that Mr. Rutherford, with a photographic 

 object-glass of llg inches aperture, has carried his process to such perfection that 

 he readily obtains impressions of stars 8£ mag., provided they are not red. It is 

 easy to obtain the image of a region one degree square. 



An Angle Measurer, by Thomas D. Smeaton. In vol. viii., p. 197, our 

 readers will find "A New Angle Measurer" described by N. J. Heineken. This 

 paper attracted the attention of Mr. Thomas D. Smeaton, of Robe, South Australia, 

 who proposes a modification, which he thinks an amateur might easily construct. 

 He dispenses with the tube shown in Mr. Heineken's drawing, and makes the wheel 

 of hard wood three inches in diameter and one inch thick. This is weighted by 

 driving a bullet in a hole at the place where Mr. Heineken puts a weight, and a\i 

 exact counterpoise is obtained by forcing shot into small holes at the back of the 

 instrument. The wooden wheel has flanges quarter of an inch high, and in its con- 

 cavity he fastens a slip of paper graduated from to 90 upwards, and from to 90 

 downwards, leaving a space between the zeros equal to the thickness of the sus- 

 pending wire. " To use the instrument, hold it between the object and the eye, 

 30 as to make the wire cover the object ; the wire will then cut the graduated 

 flange at the angle of altitude, using the upper and lower edges of the wire for the 

 corresponding gradients. Similarly the shadow of the wire will give the sun's 

 altitude." Let us take this opportunity of thanking Mr. Smeaton for sending us 

 some beautiful Australian compound polyps and polyzoa. 



Simultaneous Concealment of Jupiter's Satellites. — The Monthly 

 Notices contain an announcement by Mr. Airy of the approaching and rare 

 phenomena of the simultaneous concealment of Jupiter's four satellites. He says, 

 " On Aug. 21, Jupiter will be without satellites for one hour and three quarters." 

 At 8h. 14m. the third satellite will enter on Jupiter's face ; at 9h. 9m. the second 

 will be eclipsed ; 9h. 28m. the fourth will enter on Jupiter's face ; lOh. 4m. the 

 first will enter on Jupiter's face. Times of reappearance respectively llh. 49m., 

 12h. ISm., 12h. 23m., 13h. 54m, 



Acoustic Figures. — Cosmos describes the following method adopted by 

 M. Kundt. In a tube about a yard long and a third of au inch in diameter, pour 

 a little lycopodium powder, and shake the tube so as to distribute it equally all 



