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an egg till after the middle of May, though probably an earlycoming cuckoo may produce one sooner.
• The cuckoo makes choice of the nests of a great variety of small birds. I have known its egg entrusted to the care of the hedgesparrow; the water wagtail, the titlark, the yellow-hammer, the green linnet, and the whinchat. Among these it generally selects the three former; but shews a much greater partiality to the hedgesparrow than to any of the rest: therefore, for the purpose of avoiding confusion, this bird only, in the following account, will be confidered as the fofter-parent of the cuckoo, except in instances which are particularly specified.
• The hedge-sparrow commonly takes up four or five days in lay-. ing her eggs. During this time (generally after she has laid one or two) the cuckoo contrives to deposit her egg among the rest, leaving the future care of it entirely to the hedge-sparrow. This intrusion often occasions some discomposure; for the old hedge-Sparrow at intervals, whilft she is fitting, not unfrequently throws out fome of her own eggs, and sometimes injures them in such a way that they become addle; so that it more frequently happens that only two or three hedge-sparrow's eggs are hatched with the cuckoo's' than otherwise: but whether this be the case or not, she fits the same length of time as if no foreign egg had been introduced, the cuckoo's egg requiring no longer incubation than her own. However, I have never seen an instance where the hedge. Sparrow has either thrown out or injured the egg of the cuckoo.'
The subsequent part of the paper affords a strong inftance of the partial conduct of Nature. The individual suffers pain for. the benefit of the whole ; and one part of the system is supported by the destruction of another. The young hedgesparrows are turned out of their maternal habitation, and left cruelly to perish. It is their foster-brother that performs the unnatural deed. The fact is curious and almost paradoxical. The little animal contrives to get the bird upon its back, clambers up the side of the nest, and throws it out with a jirk. When it is two or three days old it is restless and unealy, and makes extraordinary exertions to exclude its rivals.
The egg of the cuckoo is finall, resembling the housesparrow's, and weighs from forty to fifty grains. No more than one is deposited in the same nest. The chirp of the young cuckoo is plaintive; nor does it ever acquire the adult note during its stay in this country. It feeds upon various insects and seeds. A ball of hair of the fize of a pea, and curiously wound
up, is often found in its ftomach. In this, as well as its early ferocity, it resembles a bird of prey.
Mr. Jenner promises to give a paper upon the migration of birds, which must be extremely acceptable.
Art. XV. Of the Temperament of those Musical Instruments in which the 'Tones, Keys, or Frets, are fixed, as in the
Harpfichord, Organ, Guitar, &c. By Mr. Tiberius Cavallo, F.R.S. Theoretical, writers on music have involved the science in an air of mystery. We are glad to find Mr. Cavallo treat the subject with his usual simplicity and perspicuity. The divisions of the diatonic fcale are well known. If the whole length of the musical chord be reckoned 1, the first note or C will be founded by a portion as I; the second or D by ; the third or E by f; the fourth or F by }; the fifth or G by į; the fixth or A by š; the seventh or B by 5; and the octave or c by 1. To these simple seven sounds the musicians have fince. added five intermediate notes, which are termed flats or sharps. These are, the second minor is the third minor , the fourth major 3, and the seventh major ģ. The octave can be made the key, and the other notes formed by the proportional subdivision. The fifth also, being expressed by a small fraction, ferves fometimes for the foundation of a scale which is termed the occasional key. These fundamentals give rise to two series of notes which never exa&tly coincide. The nearest interme-, diate notes are taken, and the correction which must be applied. is termed temperament. Seven octaves are nearly equal to twelve fifths ; for (3)" is nearly = (1)”. The exact value of (I)iz is 1,498, &c. and the whole chord, being divided by this number, will give the first tempered fifth, and this again the second tempered fifth, and so on. Mr. Cavallo actually tempered a monochord in this way, and tuned a harpsichord by it, which, on whatever key it was played, was harmonious throughout.
Art. XVI. Description of a new Electrical Instrument capable of collecting together a diffused or little condensed Quantity of Electricity. By Mr. Tiberius Cavallo, F.R.S. Mr. Cavallo, in a former paper, has pointed out the defects of the instruments hitherto proposed for examining small quantities of electricity. In the present he proposes an instrument which feems liable to few objections. The principle is the fame with that of Volta's electrophorus. To the shorter fides of a fat tin plate, thirteen inches long and eight broad, are foldered two tin tubes, which are open at both ends. Two glass fticks covered with sealing-wax, by means of heat are cemented into these, and support the plate în a vertical position. Two frames of wood are fastened to the bottom boards by means of brass hinges, and may be placed parallel and at the distance of one fifth of an inch from the tin plate. The application of the inftrument is easy
Art. XVII.' On the Conversion of a Mixture of dephlogisticated and phlogisticated Air into nitrous Acid, by the electric
Spark. By Henry Cavendish, Esq. F.R. S. and A. S. The beautiful experiment in which Mr. Cavendish converted into nitrous acid a mixture of the oxygenous gas and atmospheric air, by passing through it repeated electric sparks, is delicate and laborious. Several philosophers upon the continent have tried to repeat it, but without success. Mr. Cavendish therefore dia rected the experiment to be performed before some of the prinicipal members of the Royal Society, and thus completely ascertained his important discovery: Atmospheric air and oxygenous gas from turbith mineral, were confined in a bent glass tube by columns of soap-lees and quicksilver. As the acid was gradually formed, it was absorbed by the soap-lees, and produced nitre.
The oxygenous gas seems to be rather more than double of the azotic in the composition of nitre.
Art. XVIII. Experiments on the Effect of various Substances in lowering the Point of Congelation in Water. By Charles Blagden, M.D. Sec. R. S. and F. A.S. Dr. Blagden has prosecuted this subject with minute accuracy. He has made several curious remarks with regard to the appearance of the crystals formed, the transparency of the solutions, &c. which we cannot abridge. It appears that, if we denote the proportional quantities of certain salts ditsolved in water by n, the point of congelation of the solutions will be expressed by these simple formulæ: Common falt 32°-nX112°, nitre 32°-48oXn, fal ammoniac 32°-120° Xn, Rochelle salt 32°—22°Xn, fal catharticus amarus 32°~-16°Xn, green vitriol 32--10°Xing white vitriol 32° -10°Xn. These experiments seem to confirm the principle of De Luc, that the greatest cold produced by a mixture of any salt and snow is the same with which a saturated would freeze. After water has taken up as much of one salt as it can dissolve, it is still capable of diffolving a portion of a second, or even of a third falt. Dr. Blagden has found that the compound effect of these, in finking the freezing point, is nearly equal to the sum of the depressions which they could make if they were separately applied. Thus a solution of io of Rochelle falt, t common falt, and i'z fal ammoniac, congealed at 13°. The separate effects are, of the Rochelle falt =2°,2, common salt 120=11°,2, fal ammoniac '1=7o. The sum of these depressions is 20°,4, or at the point 110,6, which nearly agrees. Hence the important fact, that snow produces a more intense cold with a mixture of several falts than with a single salt. Hence also the frigorific powers of compound solutions. This has been noticed in the Memoirs of the French Academy of Sciences so far back as 1700 ; but it has lately been revived and extended.
z ENG. REV. VOL. XV. MAY 1790.
Dr. Blagden next relates the result of his experiments upon certain substances which, by equal additions, depress the freeze ing point of water in an increafing ratio. Vitriolic acid, whose fpecific gravity was 1,837 at 62°, congealed at 32°-980xn nearly; smoking nitrous acid, whose fpecific gravity was 1,454, at 32°106°Xn, nearly; muriatic acid of 1,163, at 32°—80°Xn, nearly; salt of tartar 32°-540Xn, nearly; mineral alkali, 320-21°%n; volatile alkali 32°—68oXn; spirit of wine, of the specific gravity 829, at 32°-70°xn. Water begins to expand at the temperature of 40°; and it appears that an addition of salt reduces the expansion to 8° above the depressed point of congelation.
Art. XIX. Additional Experiments and Observations relating to the Principle of Acidity, the Decomposition of Water and Phlogiston. By Joseph Priestley, LL.D.F.R.S. With Letters to him on the Subject, by Dr. Withering and James Keir, Esq. This paper contains some additional remarks upon the experiment which this ingenious philosopher made by infaming a mixture of the oxygenous and hydrogenous gases. The quantity of acid produced was so small that the doctor was at a loss to decide its species. His philosophical friends examined the liquor by various tests, and found it to be nitrous acid. We have already thewn, we hope, that this minute portion of acid is derived from the impurity of the gases, and that the experiment does not affect the theory of Lavoisier. Phlogiston is the proteus of the constitutional cheinists. It is a phantom which affumes various shapes, according to the fancy of the inquirer. Many phénomena, indeed, can be well explained by both fyltems. In the one there is an abstraction ; in the other an accumulation. But the theory which is formed upon the continent possesses a clearness, a precision, and an elegance, which set it
Art. XX. On the Probabilities of Survivorships between two Persons of any given Age, and the Method of determining the Values of Reversions depending on those Survivorships. By Mr. William Morgan. Communicated by the Rev. Richard Price, D.D.F.R.S. The hypothesis of De Moivre with regard to the probability of the duration of human life is extremely fimple, and tolerably accurate. He supposes that out of eightyfix perfons born at the same time, one dies annually till the whole number be extinguished. The chance that a person, therefore, shall attain the age of
n years is
86 85_n that of n +22
&c. Whence the chance that a 86
upon a firm basis,
that of nti,
1-1 person of the age n shall survive the present year is and the
86 chance that he shall die within the year is
By the help of these data the several problems in the doctrine of annuities can be solved with considerable elegance. But the hypothesis is particularly erroneous with regard to the early and the very advanced periods of life ; and in the case of joint-lives and of furvivorships, the errors are prodigiously increased. Recourse must therefore be had to tables of real observations. Mr. Moryan, in the paper before us, has pointed out some mistakes into which his predecessors have fallen, and has shewn the proper mode of investigation.-Suppose that the ages of two persons, A and B, were given to determine the probability of survivorship. Let A denote the number of persons living at the age of A the younger, and a', a", a'", &c. the decrements of life at the end of the ift, 2d, 3d, &c. years. Let b represent the number of persons alive at the age of B, and c, d, e, &c. those living at the end of the ist, 2d, 3d, &c. years. The event that B shall survive A during the first year may take place in two ways; either A may expire during that time, or both. The chance that A dies the first
., and that B survives that time is ; the chance, therefore, that both events take place is a The probability that both lives are extinguished during the first year
is á X 6 - 형 but the priority of the deaths is indifferent; the half of
a(6-0) this fraction, or ), will therefore express the chance that
a's a'(bc) a/b+c)
; and so on for ab 2ab
2ab the fucceffive years. Hence the whole probability of B's surviving A will be
dte a't a't a'"', &c.)
ab Mr. Morgan has taken the trouble to calculate, from these principles and the Northampton Observations, fome useful tables, which accompany this paper.
Art. XXI. An Account of a remarkable Tranfpofition of the Viscerai By Matthew Baillie, M. D. In a Letter to John