256 



HARDWICKE'S SCIENCE-GOSSIP. 



angles by another imaginary line so many degrees 

 east or west of the meridian of Greenwich. So it is 

 with the stars ; we must have their apparent places 

 indicated by the intersection of two imaginary lines 

 at right angles to each other. Instead of latitude 

 and longitude, we adopt declination and right 

 ascension. By north or south declination is meant 

 distance north or south of the celestial equator 

 (which is an extension into space of the terrestrial 

 equator), expressed in degrees, minutes, and seconds. 

 As a substitute for declination, north polar distance 

 (abbreviated N.P.D.) is sometimes employed, being 

 the distance, also in degrees, minutes, and seconds, 

 of a celestial body from the North Pole. We reckon 

 terrestrial longitude from the first meridian, an 

 imaginary line passing from north to south through 

 a certain room in the observatory of Greenwich, but 

 ior a starting-point of right ascension we must take 

 something in the heavens. That which is adopted is 

 called "the first point of Aries." About two 

 thousand years ago the sun used to enter the con- 

 stellation Aries, one of the twelve signs of the 

 zodiac, at about March 20, the time of the vernal 

 equinox, and it was at about the same date that the 

 first catalogue of the stars was made by Hipparchus. 

 This, therefore, was a convenient starting-point, and 

 though what is called "precession of the equinoxes" 

 has caused the sun's position to be other than what 

 it was at the period above mentioned, the mode of 

 reckoning has been retained. Right ascension 

 (abbreviated R.A.) is reckoned from west to east, 

 either in hours, minutes, and seconds of time, or in 

 degrees from o° to 360 . 



Our friend, wishing to show us some particular 

 object, hunts up its place in a star catalogue or in 

 the Nautical Almanack, and then explains to us some 

 of the hitherto mysterious appendages to the tele- 

 scope. He bids us notice that the polar axis (the 

 counterpart of the tilted pillar of the simple stand), 

 has, at its upper hand, another hollow axis, called 

 the declination axis, attached to it at right angles. 

 To one end of the tube moving partly inside the latter 

 the telescope is firmly fixed, to the other a mass of 

 metal, which acts as a counterpoise and tends to keep 

 everything steady. Near this counterpoise is fixed 

 at right angles to the axis a metal circle, of which 

 either the edge or the face is very accurately divided 

 into degrees and their subdivisions. A very ingenious 

 contrivance, invented in 1631 by Pierre Vernier, and 

 called by his surname, enables one to determine the 

 value of spaces much smaller than those actually 

 engraved on the circle, thereby considerably lessening 

 the difficulty and cost of workmanship. These divi- 

 sions are read by one or more microscopes conveniently 

 placed. The graduation on the circle is arranged in 

 four quarters or quadrants from o° to 90 each, and 

 the line joining o° and o° points to the celestial 

 equator. The Verniers, for there are usually two, 

 placed diametrically opposite each other, being 



attached to, and therefore moving with, the tube 

 which passes through the hollow declination axis, 

 and to the other end of which the telescope is 

 attached, can be set to any part of the declination 

 circle. By this means the telescope is set to the 

 declination of the object sought. At the lower end 

 of the polar axis are two other circles, one of which 

 is movable, with their Verniers and reading micro- 

 scopes ; these are divided into hours, minutes, etc. 

 The sidereal time is noted, one of the R. A. circles 

 is set to it, and the other to the R. A. of the object, 

 the clockwork is set going, and we can now examine 

 the object, whatever it be, at our ease. In the more 

 complete form of equatorial the reading microscopes, 

 for both declination and right ascension, have their 

 eye-pieces at the eye-end of the telescope. 



{To be continued.) 



NOTES ON VEGETABLE TERATOLOGY. 



DURING the summer months the number of so- 

 called "sports" and " monstrosities," which 

 our kind and sympathetic readers have forwarded to 

 us, has been immense. It is next to impossible to 

 thank every donor, so the will has to represent the 

 deed. At times one's study has looked like a chamber 

 of vegetable horrors — a kind of vegetable lunatic 

 asylum, where nearly everything had gone wrong ! 

 Of course, behind all this, lay hidden many suggestive 

 ideas, for the naturalist is perfectly aware that a 

 " freak " or "monstrosity" is the result of laws as 

 imperative as those of ordinary growths. The one 

 use we have suggested concerning specimens of 

 vegetable teratology is that they give us possible 

 glimpses of the phyla, or lines of genealogical 

 descent of many of the great and powerful orders of 

 the vegetable kingdom. 



But even apart from such important matters, other 

 " monstrosities " illustrate the laws of relationship 

 and convertibility of the organs of plants. They 

 prove to us how acts of specialisation have been 

 brought about — leaves converted into floral organs or 

 contrariwise. We give a selection of some of the 

 many notes furnished by correspondents. 



One of the most remarkable is a pinnated leaf of 

 Salvia, sent by Doctor Newth, of Hayward's Green. 

 It is no uncommon thing to find red or yellow 

 leaves, but in this instance they are of a brilliant 

 Prussian blue colour. In other woids, the leaves 

 have assumed the colour of the petals. 



Fasciation seems to be the easiest way in which 

 plants go wrong, and therefore we cannot wonder 

 the Nat. Ord. Composita? is the most flourishing 

 in the world. 



Mr. E. Buckell, of Romsey, sent us a very 

 remarkable example of fasciation in a species of 

 chrysanthemum, no fewer than seven or eight heads 

 being fused into one, as well as their stems. The 



