MAR 



MAR 



w 380 marriages always existing 1 together. 

 The number of survivors also arising 

 from tiiese marriages, and always living 

 together, would, in twice 57 years, in- 

 crease to the same number. Moreover, 

 the particular proportion that becomes 

 extinct every year, out of the whole num- 

 ber constantly existing together of single 

 or joint lives, must, wherever this num. 

 her undergoes no variation, be exactly 

 the same with the expectation of those 

 lives at the time when their existence 

 commenced. Thus, if it were found, that 

 a nineteenth part of all the marriages 

 among any body of men, whose numbers 

 do not vary, are dissolved every year by 

 the deaths of either the husband or wife, 

 it would appear, that 19 was, at the time 

 they were contracted, tb,e expectation of 

 these marriages. 



Dr. Price observes, that the annual ave- 

 rage ot weddings among the ministers 

 and professors in Scotland, for the last 

 twenty-seven years, has been 31; and the 

 average of married persons, for seventeen 

 years, ending in 1767, had been 667. This 

 number, divided by 31, gives 21 i, the 

 expectation of marriage among them ; 

 which, he says, is above two years and a 

 half more than the expectation of marri- 

 age would be, by Dr. Hal Ley's table, on 

 the supposition that all first, second, and 

 third marriages, may he justly considered 

 as commencing, one with another, so 

 early as the age of 30; and lie has 

 proved, that the expectation of two equal 

 joint lives, is to the expectation of a sin- 

 gle life of the same age, as two to three : 

 consequently, the expectation of a single 

 life at 30, among the ministers in Scot- 

 land, cannot be less than 32.25. If we 

 suppose the mean ages of all who marry 

 annually to be 33 and 25, the expectation 

 ef every marriage would be nineteen 

 years ; or, one with another, they would 

 he all extinct in nineteen years : the mar- 

 fiages which continue beyond this term, 

 though fewer in number, enjoying among 

 them just as much more duration as 

 those that fall short of it enjoy less. B Jt 

 it appears from the observations and ta- 

 bles of M. Muret, that, in the district 

 of Vaud (dividing half the number of 

 married persons, viz. 38,328, by the an. 

 nual medium of weddings, viz. 808) the 

 expectation of marriage is only 23^ years : 

 so much higher are the probabilities of 

 life in the country than in towns, or 

 than they ought to be, according to De 

 Moivre's hypothesis. See PRICE'S AN- 



M ARROW, in anatomy, a soft oleag/> 

 nous substance, contained in the cavity of 

 the bones. 



MARRUBIUM, in botany, horelunmd, 

 a genus of the Didynamia Gymnospermia 

 class and order. Natural order of Verti- 

 ciilatae. Labiate, Jussieu. Essential cha- 

 racter : calyx salver-shaped, rigid, ten- 

 streaked ; corolla upper lip bifid, linear, 

 straight. There are eleven species. These 

 plants are chiefly preserved in botanic 

 gardens for the sake of variety. 



MARS, in astronomy, the planet that 

 revolves next beyond the earth in our 

 system, is of a red fiery colour, and al- 

 ways gives a much duller light than Ve- 

 rms, though sometimes he equals her in 

 size. He is not subject to the same limi- 

 tation in his motions as Mercury or Ve- 

 nus, but appears sometimes very near the 

 sun, and at others at a great distance 

 from him; sometimes rising when the 

 sun sets, or setting when he rises. Of this 

 planet it is remarkable, that when he ap- 

 proaches any of the fixed stars, which all 

 the planets frequently do, these stars 

 change their colour, grow dim, and often 

 become totally invisible, though at some 

 little distance from the body of the planet ; 

 but Dr. Herschel thinks this has been ex- 

 aggerated by former astronomers. Mars 

 appears to move from west to east round 

 the earth. The mean duration of his side- 

 real revolution is 686.979579 days. His 

 motion is very unequal. When we first 

 perceive this planet in the morning, when 

 lie begins to separate from the sun, his 

 motion is direct, and the most rapid pos- 

 sible. This rapidity diminishes gradually, 

 an4 the motion ceases altogether, when 

 the planet is about 137 distant from the 

 sun ; then his motion becomes retrogade, 

 and increases in rapidity till he comes into 

 opposition with the sun. It then gradually 

 diminishes again, and becomes nothing, 

 when Mars approaches within 137 of the 

 sun. Then the motion becomes direct, 

 after having been retrograde for seventy- 

 three days, during which interval the 

 planet described an arc of about 16. 

 Continuing to approach the sun, the planet 

 at last is lost in the evening rays of that 

 luminary. All these different phenomena 

 are renewed after every opposition of 

 Mars, but there are considerable differ- 

 ences both in the extent and duration of 

 his retrogradations. 



Mars does not move in the plane of the 

 ecliptic, but deviates from it several de- 

 grees. His apparent diameter varies ex- 

 ceedingly. His mean apparent diameter 



