1847.1 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



287 



effective — this building being 363 feet in leogtb, 100 feet wide, and 03 feet 

 high. It was therefore thought desirable to ascertain if it would be possi- 

 ble to cut olf these scorching rays by the use of a tinted glass, which 

 should not be objectionable in its appearance, and the question was at the 

 recommendation of Sir W. Hooker and Dr. Lindley submitted by the 

 Commissioners of Woods, &c. to Rlr. Hunt. The object was, to select a 

 glass which should not permit those heat rays which are the most active in 

 scorching the leaves of plants to permeate it. By a series of experiments 

 made with the coloured juices of the palms themselves it was ascertained 

 that the rays which destroyed their colour, belonged to a class situated at 

 that end of the prismatic spectrum which exhibited the utmost calorific 

 power, and just beyond the limits of the visible red ray. A great number 

 of specimens of glass variously manufactured were submitted to examina- 

 tion, and it was at length ascertained that glass tinted green appeared 

 likely to effect the object desired most readily. Some of the green glasses 

 which were examined obstructed nearly all the heat rajs — but this was 

 not desired, and from their dark colour these were objectionable, as stop- 

 ping the passage of a considerable quantity of light, which was essential 

 to the healthful growth of the plants. Many specimens were manufac- 

 tured purposely for the experiments by Messrs. Chance of Uirmingham, 

 according to given directions, and it is mainly due to the interest taken by 

 these gentlemen that the desideratum has been arrived at. Every sample 

 of glass was submitted to three distinct sets of experiments — 1st. To 

 ascertain, by measuring off the coloured rays of the spectrum, its transpa- 

 rency to luminous influence. 2nd. To ascertain the amount of obstruction 

 offered to the passage of the chemical rays. 3rd. To measure the amount 

 of heat radiation which permeated each specimen. The chemical changes 

 were tried upon chloride of silver, and on papers stained with the green 

 colouring matter of the leaves of the palms themselves. The calorific 

 influence was ascertained by a method employed by Sir John Herschel in 

 his experiments on solar radiation. Tissue paper stretched on a frame was 

 smoked on one side by holding it over a smoky flame, and then while the 

 spectrum was thrown upon it the other surface was washed with strong 

 sulphuric ether. By the evaporation of the ether the points of calorific 

 action were most easily obtained, as these dried off in well defined circles 

 long before the other parts presented any appearance of dryness. By 

 these means it was not difhcult, with care, to ascertain exactly the condi- 

 tions of the glass, as to its transparency to light, heat, and chemical 

 agency (actinism). The glass thus chosen is of a very pale yellow-green 

 colour, the colour being given by oxide of copper, and is so transparent 

 that scarcely any light is intercepted. In examining the spectral rays 

 through it, it is found that the yellow is slighly diminished in intensity, and 

 thatvthe extent of the red ray is affected in a small degree, the lower edge 

 of the ordinary red ray being cut off by it. It does not appear to act in 

 any way upon the chemical principle, as spectral impressions obtained 

 upon chloride of silver are the same in extent and character as those pro- 

 duced by the action of the rays which have passed ordinary white glass. 

 This glass has, however, a very remarkable action upon the non-luminous 

 heat-rays, the least refrangible calorific rays. It prevents the permeation 

 of all that class of heat-rays which exist below and in the point fixed by 

 Sir William Herschel, Sir H. Englefield, and Sir J. Herschel, as the point 

 of maximum calorific action. As it is to this class of rays that the scorch- 

 ing influence is due, there is every reason to conclude that the use of this 

 glass will be effective in protecting the plants, and, at the same time, as it 

 is unobjectionable in point of co/our, and transparent to that principle 

 which is necessary for the development of those parts of the plant which 

 depend upon external chemical excitation, it is only partially so to the 

 heat-rays, and it is opaque to those only which are the most injurious. 

 The absence of the oxide of manganese, commonly employed in all sheet 

 glass, is insisted on, it having been found that glass, into the composition 

 of which manganese enters, will, after exposure for some time to intense 

 sun-light, assume a pinky hue, and any tint of this character would com- 

 plelely destroy the peculiar properties for which this glass is chosen. 

 Melloni, in his investigations on radiant heat, discovered that a pecu- 

 liar green glass, manufactured in Italy, obstructed nearly all the calorific 

 rays ; we may, therefore, conclude that the glass chosen is of a similar 

 character to that employed by the Italian philosopher. The tint of colour 

 is not very different from that of the old crown glass; and many practical 

 men state that they find their plants flourish much better under this kind 

 of glass than under the white sheet glass, which is novp so commonly 

 employed. 



" On the Potassium Battery." By Mr. Goodman. 



An amalgam of mercury and polassium was placed in a vessel closed 

 with a diaphragm at one end, and holding mineral naphtha. This was 

 plunged into an acid solution, or a solution of sulphate of copper, con- 

 taining a platina plate. By the action of the acid through the skin, the 

 oxidation of the potassium was efl'ected ; and by connecting these plates 

 with a voltameter, water was readily decomposed, or with a galvanometer 

 a considerable deflexion produced. 



" On a Si/stem of Colouring Geological Maps." By J. W. Salter. 



Hitherto geologists have represented the British strata by colours taken 

 from the general hue of the rock, modified by the necessity of using bright 

 tints and distinguishing adjacent formations by colours strongly contrasted. 

 Continental geologists have not entirely adopted these colours, nor is there 

 perfect accordance even in the maps of Englishmen. Mr. Salter proposed 

 to remedy the iuconreBieDce and uncertainty attending the present method 



of colouring maps by introducing a system capable of universal adoption. 

 The same colour, he says, should always be employed for the same group 

 of rocks, various shades of that common colour being suflicient to distm- 

 guish, and at the same time combine, all the subdivisions of that group. 

 Again, the colours used to designate systems of strata should follow in 

 some constant order. The chromatic scale naturally suggested itself as 

 the most harmonious gradation of colours, and accordingly Mr. Salter pro- 

 prosed to represent the Silurian strata by Violet; Carboniferous, B/ue; 

 Triassic, Gnen ; Oolitic, Yellow ; Cretaceous, Oravge ; Tertiary, Red. 

 It was necessary to use a more intense red, with the addition of various 

 markings, for the granitic rocks. 



Mr. Greenough referred to the pamphlet accompanying his geological 

 Map of England, for an exposition of the principles by which he was 

 guided,— which were approved of by the English geologists, and from 

 which the French had departed with regret.— Mr. Phillips and Sir H. 

 De LA Beche recommended the adoption of one colour for each system, em- 

 ploying engraved lines of various kinds to distinguish the subdivisions, 

 thereby diminishing the cost and increasing the accuracy of coloured maps. 

 — Sir K. I. MiiRCHisoN said he had once attempted to apply the scheme 

 now advocated by Mr. Salter, but found it, practically, less serviceable 

 than Mr. Greenough's, which was the basis of all the other maps. 



HYDRAULIC MACHINE FOR RAISING WATER, &c. 



Invented iy Michael Scott, Engineer of tie Liverpool Water Works. 

 This machine was originally planned as a substitute for the com- 

 mon air pump in marine steam engines. As such I will tirst speak of 

 it. Some years ago I was engaged in designing an engine which it was 

 desirable to compress into the smallest possible bulk. The chief diffi- 

 culty was the air pump and its attachments, which, if the ordinary 

 arrangement was adopted, would occupy valuable space and make 

 the engine complex. Observing this, I determined, if possible, to get 

 rid of this pump altogether, and with this view, designed the machine 

 as represented in fig. 1, where A is a pipe passing through the bow of 



Fig. 1. 



Fig. 2. 



the vessel, which, at a convenient distance aft, diverges into two 

 branches, which branch pipes again respectively debouch into the sea 

 near the stern. D is a double hinge valve, moveable by a brass rod 

 passing through a stuffing box on the top of the pipe. By this rod 

 the valve D may be thrown to either side of the chamber so as to shut 

 the communication between the pipe A and the pipe B or C, as the 

 case may be, on the one side, and on the other side, so as to open the 

 port between one of the pipes B or C and the pipe E, which descends 

 from the condenser. 



It will be observed, also, that there are two valves marked 1 and 2, 

 one in each pipe opening upwards, which allow the water to pass out, 

 but prevent its return. These valves may be equilibriated, and also 

 opened or shut, by a crank joined to the axle which passes through 

 the side of the pipe. So much for the configuration ; now for the 

 mode of action. Suppose the ship to be in motion (going ahead) and 

 the valve D in the position shown, then the water will rush through 

 the pipe A, and there being no obstruction offered, will pass through 

 C and out at the stern. But let us throw the valve D to the otter 



