1844.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL 



401 



tend to thrust D, further from C; l)ut the side C, expanding at the 

 same time, pushes the upper extremities of A, B, wider apart, as re- 

 presented by the dotted lines,) and, consequently, — if the length of C, 

 be properly proportioned to A, B, — D will remain at the same distance 

 from C, as before. Again, suppose A, B, shortened by cold, the length 

 of the pendulum is not effected, because the contraction of the side 

 C, draws A, B, near together, and keeps D, where it was. 



Hence it would seem that whatever variations of temperature may 

 take place, such a pendulum, if correctly made, would be invariable. 

 As the compensating property depends on the figure of the rod, no 

 adjusting apparatus would be required. In simplicity, and other 

 qualities, it surpasses the mercurial instrument of Graham, and the 

 grid-iron of Harrison — that is, if the principle be found correct, and 

 no mistakes in the inferences drawn from it. One striking defect, 

 besides that of figure, is the want of stiffness, or rigidity, an impor- 

 tant desideratum in a pendulum rod. The spring of the side C, might 

 be fatal, To obviate this, in some measure, that side might be a Hat 

 bar, or the whole might be cut out of sheet metal, in which case the 

 edges would oppose less resistance to the air. The position of the 

 instrument, as shown in the figure, might be inverted— D, being made 

 the point of suspension, and the weight placed at C. 



Such is the memorandum referred to. If it be found of little worth, 

 as regards the pendulum, it may, possibly, suggest, to some minds, 

 more valuable speculation.— iVew York, July 5, 1844. T. E.— Frank- 

 lin Journal, 



ARCHITECTURAL AND ENGINEERING PREMIUMS. 



The Society of Arts have announced the fotlou'hig premiums: — I. The 

 Gold Medallion is offered to the candidate who shall produce the best original 

 design for a town a»d county hall, containing the requisite accommodations 

 for holding assizas, a large room for public meetings, and offices for magis- 

 trates' clerk, &c ; to be sent in on or before the third Tuesday in January, 

 1845. The expense of the building not to exceed 40,000/. The drawings to 

 consist of two plans, one or more geometrical elevations, and two sections, 

 drawn to a scale of a quarter of an inch to a foot ; also a perspective view. 



2. Acton Premium. — In the year 1837, a gift of .500/. was made to the 

 society by Mrs. Hannah Acton, of IJuston-square, for the purpose of enabling 

 the society to offer an annual reward for the promotion of practical carpentry, 

 applicable to civil, naval, and military architecture. In compliance with the 

 terras of the above donation, the society offers a Gold Medallion for the best 

 design for a roof of 100 feet span and l.'iO feet in length, with the walling 

 necessary for its support. Each design to consist of a plan, and two sections, 

 neatly outUned in Indian ink, and tinted, with a scale annexed ; also a model 

 of one bay, or larger portion (as the candidate shall see fit), should accom- 

 pany the design. The model and drawings to be sent in on or before the 

 third Tuesday in January, 1845; and to become the property of the society 

 if the candidate be successful. 



3. The Gold Medallion is offered for the best design for the hull-timbers 

 of a steam-vessel of 1,000 tons burden. Such design to consist either of a 

 model or of a plan, section, and other drawings sufficient to explain the 

 same. The model or drawings to be sent in on or before the third Tuesday 

 in January, 1845 ; and to become tlie property of the society if the candidate 

 be successful. 



4. For the best original design as a subject for modelling or carving, 

 adapted to furniture or internal decoration, by an operative mechanic in 

 either of these branches of art — the Sdver Medal and i'ive Pounds. 



BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 



FocBTEENTH Mkbting, 1844. — Held at lor*.' 



The Influence of Light on the Germination and Growth of 

 Plants. — By Mr. R. Hunt. 



The author postponed a full Report on this subject untU he had been en- 

 abled by the experiments of another year to reconcde, if possible, some very 

 anomalous results. Several experiments were described, all of which went 

 to confirm the statement originally made by Mr. Hunt, that light prevented 

 healthful germination, and was detrimental to the growth of the young plant. 

 The author now gave the results of some experiments made with a view of 

 determining the question of the production of the woody fibre. He finds that 

 plants growing under the influence of light which has permeated blue and 

 red media, contains more water than those which had been grown under the 

 influence of rays which had permeated yellow and green absorptive media. 

 On the contrary, the formation of woody fibre is greatest in the plants grown 

 under the yellow and green relatively as follows : — 



1 We are indebted for the reports to the local papers and partly to the ' Atlnnseum.' 



Those under the blue leaving 7'16 per cent, of woody fibre, 



the red 7-25 



the green 7'60 



the yellow 7-69 



Young plants in a healthly state were removed from the garden to the in- 

 fluence of the isolated rays. In all cases, the plants died under the yellow 

 light in a few days; they slowly perished under the influence of the green, 

 and only grew healthfully under the red and blue light. 



Prof. Grove wished to make some inquiries relative to the supposed ex- 

 istence of a new principle in connexion with light, which was regarded by 

 Mr. Hunt and others as the active chemical agent, to which was to be 

 ascribed all the phenomena of photographic action, and the most genial in- 

 fluence on the growth of the young plant. — Mr. Hunt explained that the 

 luminous calorific and chemical spectra were capable of producing extremely 

 dift'erent effects. That the light coming from the sun was not at all equal in 

 quantity to the heat ; and that that element was much less than the amount 

 of chemical power. He showed by diagrams, that the quantity of chemical 

 power increased in the spectrum as the light diminished, and that when the 

 light was at a maximum the chemical action was at a minimum. It was also 

 stated, that by the use of absorbent media, light of great intensity could be 

 obtained, which possessed scarcely any chemical power: and on the con- 

 trary, that this chemical principle of the solar beam could be obtained in the 

 same way bu twitli a very small amount of light. 



On the Excavations of the Rocky Channels of Rivers, bv the 

 Recession of their Cataracts. 



Mr. Featherstonhaugh drew attention to the manner in which extensive 

 lacustrine and merecageous districts upon the continent of North America, 

 have been drained and rendered fit habitations for man. During his re- 

 searches in that part of the western hemisphere, he found evidences upon all 

 the rivers whose valleys were bnimded by lofty escarpments, that the gorge 

 in which each river flowed had been cut out of the land by the recession of 

 a cataract. The river Mississippi flowed in a valley of this character. From 

 the Falls of St. Anthony to its mouth in the Gulf of Mexico, the distance 

 was about 2,000 miles, during the first 1,200 of which these escarpments, 

 varying from 200 to 450 feet in height, were everywliere found, divided from 

 eacli other by a width varying from one to two and a half miles, the valley 

 being during the greater part of this coiuse thickly studded with well-wooded 

 islands, amongst which the waters of the river flowed. Upon a level with 

 the surface of these islands were extensive plains connected occasionally with 

 lateral valleys coming through the escarpments, the soil of which was iden- 

 tically the same with that of the islands, being a light vegetable sandy soil 

 much mixed up with decayed freshwater shells; showing that these soils 

 were the old muddy bottom of the river, deposited when it occupied the 

 whole breadth of the valley from escarpment to escarpment. These, and 

 analogous appearances upon the courses of other American rivers, especially 

 the immense lacustrine deposits separating Lake Erie from Lake Huron, 

 seventy miles in breadth, were adduced as proofs of a great diminution of 

 tlie quantity of fresh water once occupying the lakes, and the fluviatile 

 courses of that continent : indeed, from the difference of level between a 

 point on the Wisconsin River and the channel of the upper Fox River, over 

 which boats now pass in time of great floods, the water communication be- 

 twixt the Mississippi and Lake Erie seems to have been uninterrupted. This 

 portion of the paper was intended to show, that the quantity of water in the 

 rivers in ancient times so far exceeded the quantity flowing in them at pre- 

 sent, that the cataracts in the rivers must have been much more powerful, 

 and that therefore the process of excavation of the rocky channels of rivers 

 by the recession of their cataracts, must have been then effected in much 

 shorter periods of time than at present. From all these considerations, and 

 from the known fact that the Fallsof St. Anthony had not receded more than 

 twenty yards in the last 100 years, the author drew the deduction that the 

 whole valley of the Mississippi, from the Falls of St. Anthony to the point 

 where the escarpments terminate, had been excavated by the recession of 

 that cataract, and that the excavation had proceeded at a much more rapid 

 pace than it does in our times. The author next proceeded to explain the 

 peculiar mechanical power which streams employ in forming their channels 

 by the operation of cataracts, and divided it into two methods, the molar or 

 grinding process, most common in mountainous countries constituted of 

 primary rocks, and the subtractiny or undermining power exercised upon 

 strata of a softer quality. To illustrate the first of these methods, Mr. 

 Featherstonhaugh exhibited a beautiful pictorial view of a remarkable cata- 

 ract in the Cherokee country, called Ovnay Kay Amah, or White Water, 

 which he visited in 1837, and which had not attracted the attention of any 

 other traveller. This cataract was at a point several miles from the extreme 

 edge of the mountain, and was upwards of GOO feet high, the water falling in 

 vaiious pitches and inclined planes from the top to the bottom. Wherever 

 the water found a depression in the surface of the gneiss it lodged there, 

 and on the first fortuitous pebble coming into cavity the work of destruction 

 would begin, the current incessantly whirling about the pebble, and grinding 

 the sides of the rock until a pot-hole was formed. These were there in 

 great numbers, some of them four feet in diameter, and six feet deep. 

 Where great numbers abounded, and parietes became at length weak, and 

 giving way, all the pot holes would coalesce into one. This process being 

 repeated in various portions of the rock, the cohesion of the mass became 



