since the Argonautic expedition. But it recedes 54′′ in a year, or 1° in 72 years, and consequently 46° 44′ would require 2645 years; which reckoned backward from the beginning of 1690, will place this expedition about 25 years after the death of Solomon. But, as there is no necessity for allowing that the middle of the constellations, according to the general account of the ancients, should be precisely the middle between the prima arietis and ultima caudæ, Newton then endeavours to determine the stars through which Eudoxus made the colures pass in the primitive sphere, and by this means to fix the position of the cardinal points. From the mean of five places he finds that the great circle, which in the primitive sphere described by Eudoxus, or at the time of the Argonautic expedition, was the equinoctial colure, did, at the end of 1689, cut the ecliptic in 6° 29′ 15′′ of Taurus. In this manner, he likewise determines the mean place of the solstitial colure to be 6° 28′ 46′′ of Leo; and as this is so nearly at right angles with the former, the difference being less than half a minute of a degree, he concludes that it is rightly drawn. From this con clusion, he also infers that, from the Argonautic expedition to 1689, the cardinal points had receded from the colures 1 sign 6° and 29′; which amounts to 2627 years, allowing 72 to a degree; and these reckoned backward, as in the former case, will place the Argonautic expedition 43 years after the death of Solomon. Newton also employs other methods of a similar nature, and, by thus establishing this epoch, reduces the supposed age of the world about 500 years. Historians and astronomers of different countries and ages employ various epochs in fixing the dates of the events they record. The creation of the world; the first Olympiad; the building of Rome; the era of Nabonassar; the birth of Christ; and the flight of Mahomet, are the principal of these epochs. Many ancient authors date the occurrence of events from the Creation of the world; but the opinions of the learned relative to this primitive event do not agree with each other. This uncertainty renders the Julian period highly advantageous as a general standard to which to refer the dates of other systems, and one by which all this difference of opinion is avoided. Notwithstanding the various opinions of the learned on this subject, it should be remarked that, according to some of the most esteemed biblical critics, the sacred scriptures assign 4004 years for the interval between the creation and the birth of Christ. It is therefore easy to reduce any date of the Christian era, or of any other era when its relation to this is known, to that of the creation of the world, by means of simple addition or subtraction. The Olympiads were used by the Greek writers, as epochs to which they refer the recurrence of events. The commencement of every fourth year was the signal for the celebration of magnificent games in honour of Jupiter Olympus, at which all the states of Greece were assembled, near Olympia, a city of Peloponesus. These games were instituted by Iphitus, and the first year of the first Olympiad corresponds with the year 3938 of the Julian period, and consequently with the 776th year before the Christian era. This year was therefore the 18th of the solar cycle; the 5th of the lunar cycle; and the 8th of the cycle of indiction. From these data, any year indicated in Olympiads may easily be brought either to the Julian period, or the Christian era. we take the second year of the 87th Olympiad, which is distinguished in the history of Greece by the commencement of the Peloponesian war, as an example, we have eighty-six complete Olympiads, If which multiplied by 4, is 344 years, to which the 2 being added, we have 346 years since the commencement of the first Olympiad; but as this corresponded with the 3938th year of the Julian period, if 345 be added to this last we have 4283 for the year required. To transfer the same event to the Christian era; as the first Olympiad was 776 years before that era, we have 776-345-431 years before the birth of Christ for the date required. The Founding of Rome is the era at which the Latin writers commence their series of dates, and is therefore of general utility. According to Varro, this was the 21st of April 3961 of the Julian period, and 753 before the birth of Christ. Any year, therefore, dated according to this series, is easily brought to either the Julian or the Christian period, in the same manner as in the preceding example. The era of Nabonassor, King of the Chaldeans, is another epoch celebrated for its astronomical observations; and for having been referred to by several ancient writers on scientific subjects, particularly Hipparchus and Ptolemy. The commencement of this era corresponds to the 26th of February, of the 3967th year of the Julian period; and consequently 747 years before the Christian era. Its commencement answers to the Egyptian month Thoth; and it was then that they began their year of 365 days. The Birth of Christ is now the era adopted by all Christendom as the common point of time to which they refer the commencement of their series of dates. This is the most extensively used of any of the epochs that have been mentioned, and the dates of the one may readily be reduced to the other by means of the relations already specified. The last era abovementioned is the Hegira, or the flight of Mahomet, from which the Arabs, Saracens, Turks, Tartars, and other Mahometan writers, commence their series of dates, and corresponds to the 5335th year of the Julian period, and to the 622d of the Christian era. When an event is therefore known in any one of these systems, it is easy to reduce it to any other, by means of addition and subtraction only. Thus the present year would be expressed in the other series of dates by subtracting 622 for the Hegira, adding 753 for the era of the foundation of Rome, and 4004 for the creation. The respective dates of the present time, according to these systems, would then be 1196, 2571, and 5822. The Naturalist's Diary For JULY 1819. Deep to the root Of vegetation parched, the cleaving fields Of sharp'ning scythe; the mower, sinking, heaps THOMSON. IN consequence of the excessive heat usual in this month, an evaporation takes place from the surface of the earth and waters, and large clouds are formed, which pour down their watery stores, and deluge the country with floods, frequently laying the full-grown corn. Hay-making usually commences about this time, or rather earlier, in fine seasons. The flowers which blossomed in the last month soon mature their seeds, and hasten to decay. A new race succeeds, which demands all the fervid rays of a solstitial sun to bring it to perfection. Summer may be said to commence with this month: the meadows begin to whiten, and the flowers that adorn them are mowed down. The corn gradually assumes a yellow hue, and the colours that decorate the rural scene are no longer so numerous.' 1 See the principal parts of a Summer's day poetically described in our last volume, pp. 177-180. Towards the middle of the month, the spiked willow (spiræa salicifolia), jessamine (jasminum officinale), hyssop (hyssopus officinalis), the bell-flower (campanula), and the white lily, have their flowers full blown. The wayfaring tree, or guelder rose, begins to enrich the hedges with its bright red berries, which in time turn black. The Virginian sumach (rhus typhinum) now exhibits its scarlet tufts of flowers upon its bright green circles of leaves. The berries of the mountain ash turn red. The lavender (lavendula spica) is in flower, and affords its perfumes, whether in a fresh state, or dried, or distilled with spirits of wine. This valuable plant, for it is valuable in medicine as well as on account of its smell, will flourish in soils where other plants will not. We have heard of a piece of chalk land, of about thirty acres, in Berkshire, near Henley upon Thames, that had been tried with various articles, and would not produce any thing. At length it was planted with lavender, which succeeded beyond expectation, and the produce is sold yearly to a perfumer, who distils it upon the spot, and gives upon an average about five hundred pounds for the crop. The potatoe (solanum tuberosum) is now in flower. See our last volume, p. 180. The different tribes of insects, which, for the most part, are hatched in the spring, are now in full vigour. Pomona now offers her fruits to allay the parching thirst; currants, gooseberries, raspberries, strawberries, cherries, and cranberries, are all peculiarly refreshing at this season. Towards the end of the month, the flowers of the laurustinus (viburnum tinus), and the burdock (arctium lappa), begin to open; and the elecampane (inula helenium), the amaranth (amaranthus caudatus), the great water plantain (alisma plantago), water mint (mentha aquatica), and the common nightshade, have their flowers flull blown. The mezereon (daphne mezereon), which in Janu |