1849. 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



187 



reproduced, as it were, and exliibited in three dimensions; and he pointed 

 out the great advantage whicli the sculptor would derive from the possession 

 of dissimilar drawings of works of art, and from the study of them when 

 viewed in their true relief in the stereoscope. A Microscopic Stereoscope, 

 with several curious diagrams, was exhibited, and, in paiticular, the effect of 

 dissimilar drawings, made by the Binocular Camera, of Danneker's statue of 

 Ariadne on the Leopard, when united in the stereoscope. The united 

 image stood out in high relief as in the original statue. 



"Sequel to kis Description of a Revolving Yahjefar Locomotive and other 

 Steam-Engines." By John ANnERsoN, Esq. 



A description of this vaUe was read to the Society in 18-16. The valve 

 has a rotary in place of a reciprocating motion, and Mr. Anderson considers 

 it much more suitable for locomotive steam-engines than the common 

 valves. 



"On Improvements in the Roofs and Glazing of Conservatories and Hoi- 

 hotiscs, with a Drawing." By Mr. William Cooper. 



In this paper the author remarks that the Romans glazed their hothouses 

 with a transparent substance, called lapis specularis, a fossil of the class of 

 "talcs," with which they were chiefly supplied from the Island of Cyprus, 

 and which is used to this day by lanthorn-makers j and so good a substitute 

 is it said to have been, that the Emperor Tiberius had cucumbers at his 

 table throughout the whole year. The author gives a description of the 

 magnificent conservatory at Chatsworth, constructed by Decimus Burton, 

 Esq., architect, London, for his Grace the Duke of Devonshire, at a cost of 

 32,000/., and containing 70,000 superficial feet of glass ; and such is its 

 extent, and convenient arrangement, that three or four carriages have been 

 driven in it at one time. Instead of wooden sash-bars, the author recommends 

 wrought-iion bars, galvanised, which are by far the best and cheapest in the 

 end, inasmuch as they require no painting, and are not subject to decay, the 

 galvanised iron being an effectual remedy against the action of oxygen. 

 The expense of copper bars of sufficient strength to bear a great weight of 

 glass (especially during a hurricane, which has been proved to press at a 

 weight of 501b. per superficial inch) entirely precludes its use fur conserva- 

 tories; besides, copper for this purpose is othernise objectionable, because 

 every drop of water containing oxide of copper carries death to tlie plants. 

 Glass is now very cheap, and, instead of using panes of glass six inches 

 square, as formerly, puttied close at the joinings, and which ciuses a drop of 

 water arising from the condensed vapour, and which is injurious to the 

 plants; the author recommends sheet glass from 30 to 60 inches long, and 

 from 6 to 9 inches wide, cut to an elliptic form at the ends and overlapped, 

 and to allow one half-inch of an opening at each joining, exactly at the 

 centre of the elliptic, puttying the remainder across in the usual way, thus 

 allowing breathing room to the plants, and the escape of the superabundant 

 carbonic gas emitted from them. The author exhibited two drawings of 

 conservatories of moderate dimensions, constructed on the most improved 

 principles, with central coned roofs ; the bend of the gkss forming an arch, 

 more effectually resists a storm. The air is heated by means of tanks and 

 hot-water pipes, being the nearest approximation of artificial to natural heat. 

 The best stones for pavement are found ou the estate of Lindsay Carnegie, 

 Esq., of Kinblethmont, near Arbroath. Glass ventilators are used instead of 

 the old method of ventilation by raising the sashes, which is attended with 

 risk and inconvenience, and often with serious injury to the plants. For 

 some purposes, and for angular roofs attached to garden walls, the author 

 recommends the use of rough plate glass ^ or f inch thick, on account of 

 . its cheapness and durability. 



"Description of a Saw-Mill, intended for Colonial tise where Metal is 

 scarce and Wood abundant." By Mr. William Reid Douglas. 



It was stated that this perpendicular saw-mill is particularly adapted for 

 colonial purposes, owing to the small quantity of metal required in its con- 

 struction — that it is also much simpler and less expensive in its construction 

 than the ones in general use, and is adapted to saw either round or square 

 timber. The motion is communicated to a shaft, on the one end of which 

 is fixed a fly-wheel, on the other a crank communicating the motion to the 

 working beam, the other end of which is attached to the under part of the 

 saw-frame ; on the same shaft is fixed an eccentric, which works a catch on 

 a small ratchet wheel fixed on the end of a wooden roller, on which the 

 rope winds as it draws forward the slide bench, the motion of which can be 

 retarded by the application of pulleys, if required. 



"A Machine for Cutting down Standing Timlier, capalle of being used 

 by one man." By Mr. George D. Howell 



The macliine is intended to be useful where labour is scarce. The saw 

 being fixed in a frame, admits uf one power pressing each way alternately. 

 The body of the machine is so constructed that it may be taken to pieces, 

 and rendered portable. 



"An Improved Glazier's Machine." By Mr. George D. Howell. 



This glazing machine, by being secured by the screw underneath, was 

 stated to be less liable to shift, or to jolt, or be unsteady, as when secured 

 with the pins in present use : and by having the cross-bar padded, secures 

 the paint inside from injury by friction. The common machine, it was 

 stated, could be altered to this plan, with comparatively little expense. 



ON BOILER CRUST 



Mr. William West, of Leeds, lately read the following paper before the 

 West Riding Geological and Polytechnic Society, "On tlie Component Parts 

 of the Crust or Fur in Boilers": — " It has been common to speak of bicarbon- 

 ate of lime, or carbonate of lime dissolved in water by excess of carbonic acid, 

 according to the opinions on a theoretical point of authors describing the 

 same substance, as yielding the crust, or 'fur,' of steam boilei-s; and either 

 to deny or overlook the share which sulphate of lime has in the formation 

 of this troublesome deposit. Among those who have gone so far as to deny 

 the existence, or, at least, the practical importance, of sulphate of lime in 

 these cruses, is Dr. Ritterbandt, the proprietor of a very ingenious, and, I 

 believe, in some situations, a very effectual patent method for preventing in- 

 crustations of the carbonate, by introducing chloride of ammonium into the 

 boiler. At that temperature carbonate of ammonia is driven off, and the 

 highly soluble chloride of calcium remains, in place of insoluble carbonate 

 of lime. I have, however, so often found in these crusts not merely a nota- 

 ble, but a considerable, portion of sulphate of lime, that I liave on different 

 occasions, when my subject required, called attention to its presence, and 

 expressed an opinion, which I have found much to confirm, that it is even 

 more troublesome antl mischievous than the carbonate alone. The specimen 

 now treated of was formed, under somewhat peculiar circumstances, in a 

 low-pressure boiler. It contains not a trace of carbonate, yields not a 

 bubble of effervescence with acids, and a portion dissolved in a large quan- 

 tity of water yields, with chloride of barium, a quantity of sulphate of 

 barytes, closely equivalent to what it would furnish if pure anhydrous sul- 

 phate of lime. It contains a little oxide of iron. It is not the curious salt 

 discovered by Professor Johnstone, containing half an atom of water to each 

 atom of sulphate of lime ; for ten grains, finely powdered, lost by exposure 

 to a red heat only three-tenths of a grain — less than a quarter of an atom 

 of water, and, therefore, hygrometric or accidental ; and the sulphate is es- 

 sentially anhydrous. The deposition of sulphate oi lime from a solution, 

 far below saturation, takes place in the manner which 1 described some 

 years ago, in the Journal of the Royal Institution. As each bubble of 

 steam is disengaged during brisk ebullition, the sulphate of lime, of course, 

 separates; for its re-solution time would be required, but tiefure that can 

 take place many other particles are separated, and these rapidly cohere into 

 portions large enough to subside and to resist yet more the solvent power of 

 the water. I have elsewhere, and on other occasions, stated my belief that 

 though gypsum, in its hydrous and ordinary crystals, is asofter mineral than 

 calc spar, yet that boiler crusts containing much sulphate of lime are harder 

 than those composed wholly or chiefly ol carbonate. The present specimen 

 curiously confirms this opinion. I am assured by the workmen that not 

 only was it with difliculty removed by the tools usually employed lor sucli 

 purposes, but that even the ' sate,' or hard chisel, used for cutting cold 

 iron, is sometimes broken or turned by this crust." 



BRUNTON'S NEW COLLIERY VENTILATOR. 



At Gelly Gaer Colliery, a ventilator upon an entirely new construction, in- 

 vented by Mr. Brniiton, has been erected under his superintendence, for the 

 special purpose of testing its power of rarefiotion. On Friday the 4lli ult., 

 Thomas Powell, E-q., of the Gaer, proprietor of the colliery, together with 

 several practical and scientific gentlemen, attended to see the machine put 

 to work, and to ascertain its capability. 



The machine is applied to the top of the upcast pit by a short tunnel or 

 air-course, and is driven by a steam-engine. By the principles of this ma- 

 chine, the air is subjected to the influence of centrifugal force, whereby any 

 degree of rarefaction necessary to the complete veutilatiun of a colliery may 

 be attained with the greatest economy of power. The rarefaction produced 

 was indicated by a water gauge ; and being carefully noted and compared 

 with the velocity of the machine, was found most satisfactorily to correspond 

 with theoretical deductions. The rarefaction maintained in the upcast pit 

 being equal to 2J inches of water, or 131b. on the square foot, of course 

 produced a strong current through the workings of the colliery, one of the 

 aii--ways of which, 20 yards long, has a mean area of 9^ superficial feet ; 

 yet such was the power of the machine, that 18,000 cubic feet per minute 

 were propelled through this passage at a velocity of 32 feet per second, and 

 afterwards in its way to the upcast pit, through au opening of only 4 super- 

 ficial feet area, at a velocity of 70 feet per second, exhibiting a degree of 

 rarei'aciion and power of propulsion (the chief objects of the experiment) 

 to the entire satisfaction of all the gentlemen present. The quantity of air 

 was measured carefully in its passage through one of the levels 6 feet 

 square, where it travelled 20 yards in 7 seconds. 



The mechanism of the machine is of the most simple and integral cha- 

 racter; has no valves or separate moving parts; has no attrition, and all 

 the friction is resolved into a foot pivot moving in oil. When at rest, offers 

 no irapeduiient to the air ascending from the pit, — liable to no derangement, 

 and is very inexpensive: in short, it is a simple mechanical implement, 

 whereby any degree of rarefaction necessary to ventilation is rendered cer- 

 tain, regular, and under visible inspection, being subject to the law of central 

 forces, which is as fixed and determinate as that hy which a stone falls to 

 the earth. 



On the following day a very important experiment was made by stopping 



2a* 



