APPENDIX. 



155 



ment, when the object is at a high elevation, we 

 can view celestial phenomena with the same ease 

 as if we were sitting at a writing desk reading a 

 book. With a magnifying power of about 40 or 

 jO times applied to this telescope, terrestrial ob- 

 &amp;gt;ects appear extremely aright and well defined. 

 A speculum of 49 inches focal distance, and 6i 

 inches diameter, has lately been fitted up on the 

 same principle. With magnifying powers of 

 from 100 to 160 times, it exhibits distinct and in 

 teresting views of the moon s surface, and of the 

 ring of Saturn, and with a power of 56 times it 

 affords a beautiful view of land objects. The 

 specula used in these instruments are far from 

 being good ; being of a yellowish colour, and 

 scarcely half polished, and having large holes in 

 the centre ; as they were originally intended for 

 Gregorian reflectors ; yet the brightness of vision 

 approaches nearly to that of achromatic tele 

 scopes. The experiments which have been made 

 on this subject demonstrate, that a tube is not 

 necessary for a reflecting telescope, when view 

 ing either celestial or terrestrial objects ; and, 

 therefore, this construction of the instrument may 

 be denominated, The Aerial Reflector. The 

 simplicity of the construction, and the excellence 

 of the performance of these instruments, have 

 been much admired by several scientific gentle 

 men to whom they have been exhibited. A 

 caveat has lately been lodged at the Patent Of 

 fice, in the view of taking out a patent for this 

 construction of reflecting telescopes ; and a more 

 detailed account of it will probably soon appear 

 in some of the scientific journals. 



In the system of Optics, lately published in 

 the Edinburgh Encyclopaedia, (one of the most 

 luminous and comprehensive treatises which has 

 yet appeared on this subject,) the writer, in his 

 introduction to the account of Dr. Brewster s 

 improvement on the Newtonian telescope, re 

 marks : &quot; If we could dispense with the use of 

 the small specula in telescopes of moderate length, 

 by inclining the great speculum, and using an 

 oblique, and, consequently, a distorted reflection, 

 as proposed first by La Maire, we should consider 

 the Newtonian telescope as perfect ; and on a 

 large scale, or when the instrument exceeds 20 

 feet, it has undoubtedly this character, as nothing 

 can be more simple than to magnify, by a single 

 eyeglass, the image formed by a single speculum. 

 As the front view is quite impracticable, and, 

 indeed, has never been attempted in instruments 

 of a small size, it becomes of great practical con 

 sequence to remove as much as possible the evils 

 which arise from the use of a small speculum,&quot; 

 &c. The instruments noticed above have ef 

 fectuated the desirable object alluded to by this 

 respectable writer; and the principle of the con 

 struction is neither that of Dr. Herschel s/ron/ 

 view, nor does it coincide with that proposed 

 by La Maire, which seems to have been a mere 

 nint, which was never put intc executior. 



No. IX. p. 256. On Steam Navigation. 



The application of steam, as a mechanical 

 power for impelling vessels along rivers and seas, 

 is one of the most brilliant and useful achieve 

 ments of art which distinguish the present age 

 and seems destined to produce an important and 

 interesting change in the general intercourse of 

 nations. From the &quot; Report of a Committee of 

 Parliament,&quot; published in 1822, it appears, that 

 the first application of steam to the impelling of 

 vessels was made by an Englishman, of the 

 name of Hull, who, in 1736, obtained a patent 

 for the invention of a steam-boat, to be moved 

 with a crank and paddles. But it was only in 

 1807, that the invention was fairly brought into 

 practical use, by Mr. Fulton, an American, 

 who had the assistance and advice of Mr. Bell, 

 a Scots engineer. There are now, according 

 to Mr. Perkins* statement, about 300 steam 

 boats on the rivers, bays, and coasts of the 

 United States, varying in their size from 100 

 to 700 tons. In Britain, the first successful 

 application of steam to vessels was made by 

 the above-mentioned Mr. Bell,* who built the 

 Comet of 25 tons, and four horses power, to 

 ply on the Clyde. There are now reckoned 

 about 150 steam-boats, from 40 to 500 tons, 

 plying on (he rivers and coasts of the British 

 isles. Glasgow, which had the honour of in 

 troducing steam navigation on this side of the 

 Atlantic, is still the seat of its greatest activity. 

 According to a statement given in the &quot; Edin 

 burgh Philosophical Journal,&quot; published in July, 

 1822, there were then no less than 36 steam 

 boats, of various sizes, plying on the Clyde. 

 Some of these, besides performing regular voy 

 ages to Inverary, Campbelton, Belfast, Liver 

 pool, and other places, are also performing 

 tours, during the summer months, to the Giant s. 

 Causeway, Staffa, Skye, and other ports of 

 the Western isles, and to Inverness by the 

 Caledonian canal. Steam-boats are also plying 

 between Aberdeen and Leith between New- 

 haven and Aberdour, Brunt island, Kinghorn, 

 Kirkaldy, and Dysart; and to Queensferry, 

 Alloa, Grangemouth, and Sterling between 

 Leith and London Dover and Calais. One 

 has been plying for several years on Loch- 

 Lomond, which enables the traveller, at a small 

 expense, to take an interesting view of the di 

 versified scenery of that beautiful lake. Five 

 are just now plying on the Tay ; two of which, 

 with engines of 30 and 40 horse powers, and 

 fitted up with elegant accommodations ply daily 

 between Perth and Dundee; each of them, during 



* It is much to be regretted, and it is certainly not 

 congenial to the liberal spirit of the age, that this 

 gentleman, who was among the first inventors of 

 steam navigation, and who has done so much to 

 promote its success in the neighbourhood of Glas 

 gow, has never received any public reward for his 

 exertions, and has been left to sink into a state ap 

 proaching to poverty. 



