18JG.] 



THE CIVIL P:NGINEER and ARCHITECT'S JOURNAL. 



ir: 



Consequences in sti/le. 



Oq the former principle thfse conditions may be called causes of dis' 

 linctness. Tliey are ciinipatible will), and therefore invite the introduction 

 of, all (agreeable) qualities which iu nature can be appreciated only by 

 near inspection. Such qualities uow become characteristic of the style, 

 for the above external conditions— involving a just adaptation of technical 

 means, not only permit, but require that every excellence which was iu- 

 admissable or unattainable under other circumstances, should now assert 

 its claims. ()u the same principle, provided the work can be seen with 

 perfect convenience, the means before employed to counteract indistinctness 

 may now be thrown aside — not merely as unnecessary, but because Ihey 

 may interfere with the complete representation of a new order of facts. 

 These appear to be the general principles of the school of the Netherlands, 

 especially in subjects of figures. The leading qualities which are the 

 result may be thus enumerated. 



The assumed near point of view, permits and invites the iutroduction of 

 a large proportion of low tones, all the gradations of which are now ap- 

 preciable. These are rendered luminous by intenser but still transparent 

 shades and acquirn richness from the scarcity of strong light. Accidents 

 of light — not excepting sun-light, are admissable, and often even desirable; 

 they are no longer in danger of interfering with the intelligible represen- 

 tation of form and colour, and may be necessary to give that degree of 

 interest which the subject cannot always command. 



The employnu'nt of perspective and foreshortening is unrestricted; the 

 last appears to be avoided in no case in which it would be intelligible in 

 nature. \'arielies iu the place or " position" of objects are especially 

 Bought in depth. 



An assemblage of broken, harmonious, and nameless hues is next to be 

 remarked, among which the slightest approach to what is called positive 

 colour is efleclive. This sobriety has nevertheless the elfVct (with oc- 

 casional exceptions in the school) of giving a predominant impression of 

 warmth, and of thus vindicating the general character of colour as distin- 

 guished from mere chiaro-scuro. 



The varieties of sharpness and softness in the boundaries of forms and 

 in their internal markings, must ever exist where there is a background 

 and light and shade; the relation between them is therefore the same as 

 on a larger scale, but the extreme diminution of figures in cabinet pictures 

 generally induces utmost precision in the sharper parts. Lastly, where 

 each object may be discerned without difficulty, yet by means of delicate 

 gradations of light can keep its place and thus be easily intelligible, details 

 may be copious and forms altogether individual. Thus is again furnished 

 the link between appropriate technical means and the choice of incidents, 

 and hence the predilection with the masters of this style for familiar and 

 even trivial circumstances. On this last point it is however to be remarked, 

 that where so much juiigment and well-directed skill are present in the 

 work, our respect is commanded even by the unpretending nature of the 

 subjects ; and where these are not offensive, they cau hardly be said to 

 diminish the satisfaction of the spectator who is alive to the higher objects 

 of the artist. A greater danger to which this style is liable (in finished 

 pictures where human actors form the subject), is that of making the 

 accessories aud inanimate objects truer to nature than the representation 

 of life. This defect is, however, avoided, even iu elaborate works, by the 

 best masters of the school. 



To conclude; the resources, whether abundant or limited, of the imita- 

 tive arts are, iu relation to nature, necessarily incomplete; but it appears 

 that, in the best examples, the very means employed to compensate for 

 their incompleteness are, in each case, the source of a characteristic per- 

 fection and the foundation of a specific style. As it is r. ith the arts com- 

 pared with each other, so it is with the various applications of a given art; 

 the methods employed to correct the incompleteness or indistinctness which 

 may be the result of particular conditions are, in the works of the great 

 masters, the cause of excellences not attainable, to the same extent, by any 

 other means. In the instance last mentioned— the school of the Nether- 

 lands — it is apparent that no indirect contrivances or conventions are ne- 

 cessary to counteract the effects of indistinctness ; on the contrary, all that 

 Would be indistinct in other modes of representation is here admissible 

 with scarcely any restriction. The incompleteness overcome, which is here 

 the cause of peculiar attractions, therefore resides solely iu the conditions 

 and imperfections iu the art itself, which, on near inspection, are in greater 

 danger of being remembered. These are a flat surface and material pig- 

 ments ; and these are precisely the circumstances which, by the skill of the 

 artists in the works referred to, are forgotten by the spectator. The conse- 

 quences of the d.lliculty overcome are, as usual, among the characteristic 

 perfections of the style. 



The two extremes of "external conditions" and their corresponding 

 styles have been here chiefly considered. The intermediate modes and com- 

 binations are innumerable; but in considering the question to what extent 

 and in what respects the extremes of style may be tomp.itible with each 

 other, it will appear, on a review of what has been stated, that the grander 

 view of nature and of the technical means fitted to represent it may be satis- 

 factory in reduced dimensions in the department of form rather than in 

 those of colour and light and-shade ; and ihat, on the other hand, the com- 

 bination of the usual characteristics of small pictures with large diuicn-ions, 

 if possible in light-and-shade and colour, is impossil.le in fjim. The last- 

 named attribute being the indispensable medium of the artists' conceptions, 

 it follows that the interchange of subjects fitted respectively for the two 

 styles can only be admissible as regards the trealmeut of grand subjects 



in small dimensions, and even then at the risk of the conventions of the 

 grander style being too apparent. 



ON THE QUALITY OF LIME PRESERVED FOR FRESCO 

 PAINTING. 



By Professor Faraday. 



Led by the statement that the keeping of the lime in a slaked conditioa 

 for a couple of years is a great advantage to it, I took some specimens from 

 the stores which have been so laid up at the Houses of Parliament, for 

 the purpose of examining them in this respect. It appears to me that this 

 lime (which is in a stdte of paste) is in a very soft and sniouth condition 

 in comparision with what would probably be the condition of the lime re- 

 cently slaked ; a condition which seems to be due to its thorough disinte- 

 gration as a mass, and its separation particle from particle. On analysing 

 it I found that it contained a little carbonic acid, but not much ; for in 101) 

 parts of the dry substance there were but 5^ parts of carbonic acid ; these 

 100 parts, therefore, would contain 88 parts of quick or uncarbonated 

 lime, and 12 parts of carbonated lime, which considering the processes of 

 burning, carry ing, slaking, &c., that it had to go through, and the necessary 

 time of exposure to air before it was laid up in store, is a very small pro- 

 portion. I do not believe that the lime, which is more than 4 inches in, 

 from the exterior, has received any portion of carbonic acid during the two 

 years of its inhumation. 



In respect of the etiect of keeping lime for a time, I am led to think, 

 without however having formed any strong opinion on the subject, that the 

 benefit is due to the fine texture which it gradually acquires ; and as there 

 is no doubt that if two surfaces were prepared, the one with fine sand and 

 lime in particles comparatively coarse, and the other with the same kind 

 of sand and lime in particles comparatively far more perfectly divided, 

 that these two would act very differently both as to the access of carbonic 

 acid from the atmosphere and the transition of lime dissolved in the mois- 

 ture of the mass from the interior towards the surface; so there is every 

 reason to expect that there would be a dilTerence in the degree ofactioa 

 upon the colours at that surface, and also in the time at which that action 

 would come to a close. 



WOOBCROFT'S SCREW PROPELLER. 



WOODCROI^T r. SMITH. 



The Judicial Committee of the Privy Council met March 11, Lord 

 Brougham, Dr. Lushington, the Duke of Bucrleuch, and Lord Cottenhaiii 

 being the members present, to decide upon an application for the extension 

 of bis patent made by Mr. Woodcroft, the inventor of a particular form of 

 screw propeller. 



Mr. Jervis appeared to support the application ; and the Solicitor-Gene- 

 ral, besides waichiug the proceedings on behalf of the Crown, appeared 

 in opposition ou behalf of Mr. Smith and the Ship Propelling Company, 

 who have adopted his patent. 



Mr. Jervis, iu stating the case for his client, said, that the invention for 

 which a renewal of his patent right to which application was now made, 

 dift'eied entirely from every other kind of propelling screw in existence. 

 It was formed on the principle of a spiral, represented by the winding of a 

 circular hue round a cylinder. The patent was granted iu March 1832, 

 and he now applied to their Lordships for an extension. The history of 

 patents for screw propellers (of which he enumerated the advantages) was 

 as follows: — In 1794 Mr. Littleton had takeu out the first patent for an 

 invention of that kind, which he proposed working by band with the cap- 

 stan, and which was to be either partially or totally immersed iu the water, 

 according to circumstances. The next patent for a screw was Mr. Shor- 

 ter's, taken out in July, 1800. It consisted of the two vanes of a smoke- 

 jack, not submerged, and adapting itself to the movement of the vessel by 

 a universal joint. In ISl.i Jlr. Trevethic proposed the Archimedean or 

 fixed screw, working in a cylinder. In July 1810, Mr. Millington got a 

 patent for the application of a smoke jack placed beyond the rudder, and 

 worked with the universal joint. Iu February, 1S25, Mr. I'erkins patented 

 an invention for having two vaues, working in opposite direciions, placed 

 at the side of ihe rudder. In I82'J, Mr. Commcraux patented a perfect 

 one-turn screw fixed paralhl to the keel, and held by a stage erected for 

 that purpose beyond the rudder. The date of Mr. U oodcroft's patent was 

 in March, 1S32, and the difl'erence between his spiral and the screw of his 

 predecessors was, that whereas the former consisted of a straight line coil- 

 ed round a cylinder, the latter was made by a circular line so coiled round. 

 The effect of this invention has been to economize the power of the engine, 

 to destroy the vibration, and to produce a greater speed with fewer revo- 

 lutions. If a spiral worm was coiled round a cy linder, the angle given 

 thereby would decrease, and the " pitch" therefore increased throughout 

 the length of the shaft. Mr. Woodcroft, in his spi-cificalion, proposed ap- 

 plying this " spiral" in d.fferent parts of the ship, and amongst ether places 

 before the rudder-post, by cutting away a part of the bull. Mr. Smith's 

 patent, which wms on the application of a perfect screw of one turn placed 

 in the centre of the dead wood, was takeu out in May, 1830. In 1837 

 Mr. Ericson patented an invention which dilTered from that of Mr. Perkins 



