CCS 



SOLAR SYSTEM, MOTION OF THE. 



SOLDERING. 



CCS 



' should continue until the orbit (preserving the same major axis) 

 should be so elongated that the ultimate approach to and recession from 

 the sun should give our planet the alternate climates of Mercury and 

 Mars, and thus no doubt destroy it as the abode of beinga constituted 

 like ourselves. It is found, however, that the following relation must 

 exist : If at any one moment the square of the eccentricity of each 

 planet be multiplied by its mass and the square root of its mean 

 distance from the sun (represented in numbers), the sum of all these 

 products must be the same as it was at any moment past, or will be at 

 any moment future. And if in each product the tangent of the incli- 

 nation to a fixed plane be substituted for the excentricity, the result- 

 ing equation is true. From such relations as these, and others con- 

 nected with them, it is shown that so far as the mutual actions of the 

 planets are concerned, no one excentricity nor inclination can increase 

 indefinitely, but all their changes must be periodic, and confined within 

 rather small limits. The approach of the ecliptic to the equator, for 

 instance, which amounts to about half a second in a year (and which 

 leads speculators sometimes to talk about a past time when the 

 ecliptic passed through the pole, and a future time when it will 

 coincide with the equator), must stop long before the ecliptic reaches 

 the equator, and attain a minimum inclination, after which the two 

 will begin to separate ; the whole oscillation being less than three 

 degrees. The whole result is summed up thus : As far as terms of 

 the second order (inclusive) in the disturbing forces, and as long as 

 only the mutual attractions of the planets act, there is a mathematical 

 certainty that the Solar System will remain in its present state, the 

 elements of the different orbits oscillating about certain mean values, 

 from which they are never very distant : except only the longitudes of 

 the nodes and perihelia, which change with velocities which are always 

 very near to certain mean velocities. The probability is very small 

 that the higher dimensions of the disturbing forces would affect this 

 result, and certainly only in a length of time to which the longest 

 periods known are trifling in comparison. 



This last point, however, is of the less importance, since it has 

 become highly probable, within the last few years, that an external 

 cause does exist, which must, unless there be a counteracting force of 

 which we know nothing, in time cause the destruction of the System. 

 If the planets move in any medium which resists their motions, how- 

 ever little, the consequence must be a gradual diminution of their 

 mean distances from the sun, and a gradual increase of their velocities, 

 ending in their absolutely falling into the sun. For the presumption 

 in favour of the actual existence of such a resisting medium, see 

 COMET. This retarding agent seems to show a rapid effect upon so 

 attenuated a mass as Encke's comet, though thousands of years have 

 elapsed without its producing any sensible effect upon the planets. 

 Little as it may concern us directly, these speculations have an 

 interest, both as to the glimpse they give of the possible destiny of 

 our System, and from their association with the history of past and 

 the hope of future discovery. It is to be remembered that no science 

 has drawn out so much of mathematical talent, or indirectly excited 

 such an influence upon other branches of physical research, as the 

 application of the theory of gravitation to the development of the 

 planetary motions. 



SOLAR SYSTEM, MOTION OF THE, IN SPACE. One of the 

 most interesting results of modern astronomical research consists in 

 the discovery of the fact, that many stars of the class styled fixed stars, 

 are in reality subject to a minute movement, in virtue of which their 

 positions in the celestial sphere are slowly shifting from year to year. 

 This proper motion was originally found to be applicable only to a few 

 of the principal stars, but as the observations of astronomers have acquired 

 a greater degree of precision, the number of stars which appear to be 

 slowly changing their position continues to increase, and the probability 

 if, that there is no star in the celestial sphere whose position is absolutely 

 fixed. But the results at which astronomers have arrived with respect 

 to the parallax of the stars, combined with the relative intensities of 

 the light of the sun and the stars, as determined by photometric 

 experiments, tend strongly to confirm the idea that the sun is neither 

 more nor less than a star. It is reasonable then to suppose that the 

 sun, like the stars, should be subject to a motion of translation in 

 space. This idea seems to have first suggested itself to Foutenelle, 

 who refers to it in a notice on the labours of Cassini. Bradley also, at 

 the close of bis paper in which he announces the discovery of the 

 nutation of the earth's axis, has remarked that the apparent motion of 

 the stars may arise either from a real motion of the stars themselves, 

 or from a motion of the solar system in space. But he was of opinion, 

 that ages would elapse before astronomers would arrive at a definitive 

 conclusion on this subject. 



Thomas Wright, in his ' Theory of the Universe," published in 1750, 

 suggests, as very probable, that the sun, with his attendant planets, 

 may be circulating round some other centre. Mayer was the first 

 astronomer who endeavoured to deduce a trustworthy result from an 

 examination of the proper motions of the stars. His researches were 

 based upon a comparison of the places of eighty stars, as observed by 

 Homer in the year 1706, with the corresponding places as determined 

 by Lacaille and himself about the middle of the same century. The 

 conclusion at which he arrived was, that the proper motions of the 

 stars do not afford any evidence of a motion of the solar system in 

 [>ace. A remark made by Mayer on this occasion is worthy of 



mention. He states, that if the solar system is advancing to any par- 

 ticular region of the heavens, the stars in this direction will necessarily 

 be gradually receding to a greater distance from each other, while, 

 again, those in the opposite direction will appear to be drawn closer 

 together. In 1783 the elder Herschel having been induced to examine 

 the subject, arrived at a result quite different from that obtained by 

 Mayer. His investigation was founded on the proper motions of seven 

 of the brightest stars, as determined by Maskelyne. The result of his 

 inquiry indicated a motion of the solar system towards a point in the 

 heavens near the star \ Hercules, which he found to be situated in 

 257 of right ascension, and 25 north declination. In 1805 he subse- 

 quently resumed the subject, and obtained for the point towards which 

 the solar system is moving, the following co-ordinates : right ascension,' 

 245 52' 30" ; north declination, 49 38'. 



The same subject was considered about the same time by PreVost 

 and Kliigel, whose results agreed tolerably well with those obtained by 

 Herschel. On the other hand, Biot and Bessel, who examined the 

 subject, arrived at the conclusion that the present state of our know- 

 ledge respecting the proper motions of the stars is insufficient to afford 

 any trustworthy indication of the existence of a motion of the solar 

 system in space. In recent times, however, the researches of Arge- 

 lander, Lundahl, and Otto Struve, have confirmed the views of Sir 

 William Herschel. The researches of these astronomers were based 

 upon an examination of the proper motions of stars chiefly in the 

 northern hemisphere. The late Mr. Galloway, however, obtained very 

 nearly the same result by an examination of the proper motions 

 observed in the southern hemisphere by Lacaille about the middle of 

 the last century, and again by Johnson and Henderson iu recent times. 

 By combining his own result with the results arrived at by Argelander 

 and Lundahl, he obtained the following values for the co-ordinates of the 

 point in the heavens towards which the solar system is advancing : 



Right Ascension . 259 9''4, 

 Declination N. . 34 36''5, 



these numbers referring to the equinox of 1 792. 



The most recent examination of this subject is due to Mr. Airy, who 

 by a method totally different from that employed by previous inquirers 

 has obtained a result agreeing very nearly in right ascension, but 

 differing considerably in declination, from that hitherto arrived at. 



SOLDERED JOINTS. When two pieces of metal of the same or 

 of different natures are joined by the interposition of another metal 

 of a more fusible character than that of the pieces to be joined, it is 

 said that they are saldered together, or occasionally that they are brazed 

 together. Thus, when lead has to be joined to lead, the surfaces of 

 contact are scraped perfectly clean, and a mixed metal, composed of 

 about | of tin to of lead, is melted over the joint so as to effectually 

 adhere to the respective surfaces. When lead has to be joined to 

 brass, the soldering metal is usually composed of a mixture of 7 parts 

 of tin to 5 of lead, and this alloy is also used for soldering tin pipe, 

 or for repairing the joints of tinned iron-ware. When iron plates are 

 joined together by soldered joints, or wheu copper, tin, or lead pipes 

 are joined to iron work, the brazing or soldering metal used is com- 

 posed of about 4 parts of zinc to 3 of copper, or more properly speaking, 

 of 2 parts of fine brass to 1 of zinc, the brass consisting itself of 2 of 

 copper to 1 of zinc. The joints themselves may be either butt joints, 

 lapped joints, spiggot joints, crossed, or flat joints. Wrought-iron 

 joints upon wrought-iron are made by welding, as also are the joints 

 of wrought-iron upon steel, whenever it is possible to place the 

 respective pieces in the smith's forge ; the more unmanageable joints 

 are usually brazed. 



SOLDERING is the process of uniting the surfaces of metals, by 

 the intervention of a more fusible metal, which, being melted upon 

 each surface, serves, partly . by chemical attraction, and partly by 

 cohesive force, to bind them together. In the ordinary soldering, the 

 alloy used as a solder must be more fusible than the metals to be 

 united, and must have a strong affinity for them. To insure perfect 

 union between the solder and the surfaces to which it is applied, it 

 is essential that they be made perfectly clean and free from oxide, and 

 that the atmosphere be excluded during the operation. This is 

 effected in various ways, but most commonly by the use of borax, sal 

 ammoniac, or resin, either mixed with the solder or applied to the 

 surfaces to be joined. 



The kinds of solder used for the several metals are given under 

 SOLDERS. 



Articles of wrowjht-iron, and some qualities of steel also, may be 

 soldered with cast-iron ; the cast iron being repeatedly heated and 

 quenched in water, by which it becomes sufficiently friable to be beaten 

 to a coarse powder with an iron pestle and mortar. In making fine 

 steel instruments, gold, either alone or with a slight alloy of copper, is 

 often used as solder. Silver solder, being less expensive, and nearer 

 the colour of the steel, is preferred by some for this purpose. In 

 larger articles of iron and steel, a solder consisting of equal parts of 

 tin and iron is sometimes used. 



Common plumbers' solder is made of two parts lead and one part block 

 tin; or of the same metals mixed in nearly equal quantities; bismuth 

 is added when it is desired to make the alloy more fusible. Soft 

 solder has two parts tin to one lead ; and other alloys of tin, lead, and 

 bismuth, are used for uniting various articles of lead, tin, pewter, and 



