« AnteriorContinuar »
to pass without being observed at all. Jupiter should therefore be carefully observed for several minutes before the eclipse is expected to take place. The observer should also be furnished with a watch, previously well regulated to mean time at the place of observation. Then, if the observed time of the eclipse be found to be greater than the time at Greenwich, as inserted in the tables, the place will be situated on the east of that meridian, and consequently the difference will be the east longitude of the place; but if the observed time be less than that stated in the tables, the place will be west, and their difference will be its longitude.
The eclipses most proper for the determination of this important problem, are those of the first and second satellites, as the theory respecting them is the most accurate; and these may be easily distinguished from the others by means of the configurations given in the 12th page every month in the Nautical Almanac; which exhibit the appearances of these satellites, both with respect to each other and their primary, at the time they are most likely to be observed. It should also be observed that the immersions are visible only from the time of Jupiter's conjunction to his opposition; and the emersions only from his opposition to his conjunction. The term immersion, as here used, signifies the instant in which the satellite disappears by entering into the shadow of Jupiter; and that of emersion implies the moment of its reappearance. These eclipses generally take place at some distance from the body of Jupiter, except near his opposition to the Sun, when the satellite approaches near to the body of the planet. Before this opposition, both the immersions and emersions happen on the west side of Jupiter, but, after the opposition, on the east side.
[To be continued.]
The Naturalist's Diary
For AUGUST 1820.
And golden harvests all the surface spread. We have commonly fine weather in August, and this is particularly desirable, that the principal source of the farmer's wealth may be safely housed.
Now o'er his corn the sturdy farmer looks,
"There are some exceptions. In the year 1799, perpetual rain rendered the country in August as green as it usually is in May. Many thousand acres of wheat and other grain were covered with water. The rivers overflowed, and swept away the produce of whole farms; and a great scarcity of bread ensued.
The easy wain descends half built, then turns
About the 11th of August, the puffin (alca arctica) migrates. Priestholme, or Puffin's Island, about three quarters of a mile from the Isle of Anglesea, abounds with these birds; and their flocks, for multitude, may be compared to swarms of bees.
In the middle of the month, the swift disappears, and probably migrates to more southern regions. Rooks begin to roost in their nest trees, and young broods of goldfinches (fringilla carduelist appear; lapwings (tringa vanellus) and linnets fringilla linota) congregate; the nuthạtch chatters; and, towards the end of the month, the redbreast is again heard.
At the beginning of August, melilot (trifolium officinale), rue (ruta graveolens), the water parsnip (sysimbrium nasturtium), horehound (marrubium vulgare), water-mint (mentha aquatica), the orpine (sedum telephium), and the gentiana amarella, have their flowers full blown. The purple blossoms of the mealow saffron (colchicum autumnale) now adorn the ow moist lands. The number of plants in flower, lowever, is greatly lessened in August, those which loomed in the former months running fast to seed. 'et, we are continually reminded of the bounty of ir Creator; though the flowers of spring and the rely rose are no more, the fruits of summer and of tumn now pour in their abundant stores.
Heaths and commons are now in all their beauty; the flowers of the various species of heath (erica) covering them with a fine purple hue. Ferns also begin to flower, the commonest sort of which is the fern or brakes (polypodium filix-mas); but the female (pteris aquilina) is the most beautiful plant.
Insects still continue to swarm; they sport in the sun from flower to flower, from fruit to fruit, and subsist themselves upon the superfluities of nature. The white-bordered butterfly (papilio antiopa) appears about the beginning of August, lives through the winter, and appears again in the spring, in company with papilio io, the peacock butterfly, &c. There is something very extraordinary in the periodical but irregular appearances of this species, edusa and cardui. They are plentiful all over the kingdom in some years; after which, antiopa in particular will not be seen by any one for eight or ten or - more years, and then appear again in as great abundance as before. To suppose they come from the continent is an idle conjecture, because the English specimens are easily distinguished from all others by the superior whiteness of their borders. Perhaps, their eggs in this climate, like the seeds of some vegetables, may occasionally lie dormant for several seasons, and not hatch, until some extraordinary, but indiscovered coincidences awake them into active life'. Papilio antiopa was in great abundance in the year 1792; but scarcely a single specimen has been seen since that time. P. cardui was common in 1808, but very scarce till 1818. P. edusa was common in the years 1808, 1811, and 1818; but, in some seasons, scarcely a single specimen has been observed.
Above the sovereign oak, a sovereign skims,
- CRABBE. Some of the Chinese butterflies, called, in the language of the country, 'flying leaves,' have such shining colours and are so variegated, that they may be truly called 'flying flowers;' and, indeed, they are always produced in the finest flower gardens. .
In their own bright Kathaian bowers,
LALLA ROOKH. The caterpillar of the death’s-head, bee-tiger, jessamine-hawk, or potatoe-moth ( sphinx atropos), is found about this time upon potatoes, artfully concealing itself in the daytime on those parts of the stems of the plants which are best covered with overshadowing leaves. They are sometimes found also upon green elder and jessamine. A specimen of this
* Haworth's Lepidoptera Britannica.