other; whence the ratio between the dark and enlightened parts becomes known. But as the diameter of the planet is supposed to be divided into 12 digits, and the breadth of the enlightened part is generally expressed in the same divisions, the ratio between these areas may readily be expressed in numbers, For by finding the area of the semi-ellipse of which both the transverse AD and the semiconjugate axis CF are given, and either subtracting it from the area of the semicircle, or adding it to that area, as EF is less or greater than EC, and the result will be the area of the enlightened part, expressed in square digits: and this area subtracted from that of the whole circle will give the area of the dark part of the disc in the same terms; and consequently the ratio between them is not only known, but also expressed in the most familiar terms. The same reasoning applies equally to Mercury as to Venus; but as the former planet is so near the Sun as to present few opportunities for ob servation, on account of the intensity of the solar light, the calculation is seldom applied to him, and we have therefore not included the appearances of this planet under the head of Astronomical Occurrences. [To be continued.] The Naturalist's Diary. For JANUARY 1819. Now Cacias sends His cutting winds, his storms of hail, and snow, THE most intense cold in England is usually felt in the month of January, and the weather is either bright with frost or foggy with much snow *. The inclemency of the season now compels the numerous tribes of birds to quit their retreats in search of food. The red-breast (sylvia rubecula begins to sing. The robin has been frequently celebrated for his social disposition in entering the habitations of man; the following lines give a pleasing picture of him in the garden: Attendant on my garden's winter cares, J. PLUMPTRE2. This is the season when the ice-houses of gentlemen in the country, and the cellars of confectioners in London, are filled with ice. Some account of the construction of an ice-house may be acceptable to our readers. The situation of an ice-house ought to be towards the south-east, on account of the advantage of the morning sun in expelling the damp air, which is far more prejudicial to it than warmth The best soil on which such a house can be erected,. is a chalk-hill, or declivity, as it will take away the waste water, without the aid of any artificial drain; but where such land cannot be procured, a loose stony Of this phenomenon, and its important services to vegetation, we have already spoken at large in our former volumes. 2 For some interesting particulars of the robin, consult our last volume, p. 21. earth, or gravelly soil on a descent, is preferable to any other. For the construction of an ice-house, a spot should be selected at a convenient distance from the dwelling-house. A cavity is then to be dug in the form of an inverted cone, the bottom being concave, so as to form a reservoir for the reception of waste water. Sould the soil render it necessary to construct a drain, it will be advisable to extend it to a considerable length, or, at least, so far as to open at the side of the hill or declivity, or into a well. An air-trap should likewise be formed in the drain, by sinking the latter so much lower in that opening as it is high, and by fixing a partition from the top, for the depth of an inch or two into the water of the drain, by which means the air will be completely excluded from the well. A sufficient number of brick piers must now be formed in the sides of the ice-house, for the support of a cart-wheel, which should be laid with its convex side upwards, for the purpose of receiving the ice; and which ought to be covered with hurdles and straw, to afford a drain for the melted ice. The sides and dome of the cone should be about nine inches thick, the former being constructed of steened brick-work, that is, without mortar, and with the bricks placed at right angles to the face of the work. The vacant space behind ought to be filled up with gravel, or loose stones, in order that the water oozing through the sides may the more easily be conducted into the 'well. The doors of the ice-house should likewise be so formed as to shut closely; and bundles of straw ought always to be placed before the inner door, for the more effectual exclusion of air. The ice to be deposited in this building should be collected during the frost, broken into small pieces, and properly rammed down, in strata of C about one foot thick, so that it may become one complete body. In those seasons when sufficient quantities of ice cannot be procured, snow may be substituted, and preserved in a similar man ner'. The fields are now clothed in their winter livery, and present a novel and agreeable spectacle to the eye. Some pretty lines on two greyhounds playing in the snow form an interesting description of the scenery of the month of January. Level no more! The jetty pair, The lightest things of earth or air, Now leaning o'er the brook, with eye And that pats paw the freezing rill To try if it be water still; Then rushing to their mistress' feet, With fond caress her smile to meet. About the beginning of the month, larks (alauda arvensis) congregate, and fly to the warm stubble for shelter; and the nut-hatch (sitta europea) is heard. The shell-less snail or slug (limax) makes its appearance, and commences its depredations 1 For some observations on the use of ice and snow in cooling liquors, we refer to our last volume, p. 211. on garden plants and green wheat. The missel thrush (turdus viscivorus) begins its song. The hedge-sparrow (sylvia modularis) and the thrush (turdus musicus) begin to sing. The wren, also, pipes her perennial lay,' even among the flakes of snow. The titmouse (parus) pulls straw out of the thatch, in search of insects; linnets (fringilla linota) congregate; and rooks (corvus frugilegus) resort to their nest trees. Pullets begin to lay; young lambs are dropped now. The house sparrow (fringilla domestica) chirps; the bat (vespertilio) appears; spiders shoot out their webs; and the blackbird (turdus merula) whistles. The fieldfares, red-wings, skylarks, and titlarks, resort to watered meadows for food, and are, in part, supported by the gnats which are on the snow, near the water. The tops of tender turnips and ivy-berries afford food for the graminivorous birds, as the ringdove, &c. Earthworms lie out on the ground, and the shell-snail (helix nemoralis) appears. See some lines to the snail in our last volume, p. 23. Mr. Gisborne, in his Walks in a Forest,' draws a lively picture of cattle going to their ac customed pools to drink, when completely frozen over, and of their awkward attempts to obtain the grateful beverage. Sunk in the vale, whose concave depth receives When the shower beats, yon pool with pallid gleam |