172 



•iTHE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[M^ 



Mj. Latilla, with much apparent reason, seems to think that it was executed 

 with a mixture of wax and oil ; and lie has applied this mixture with success 

 in the banqucttiug-room of the Duke of iieaufort's mansion, in which he 

 has happily united the freshness, brilliancy, and freedom from glare of 

 fresco, with the richness and facility of oil. Mr. Latilla's process is a good 

 one, and one deserving of greater extension ; but we do not think that it is 

 the ancient encaustic, if, indeed, the discovery of the true encaustic be not a 

 chimera which, if found, would not be worth the finding. From all we have 

 seen, we fear it would be so. 



Tempera was practised by the Egyptians and the Greeks, and also in the 

 English cathedrals ; and, according to ^'asari, was executed with yolk of egg 

 mixed up with the milky juice of the tig-tree, and then used with colours ground 

 up in water. Mr. Latilla says that the fig-tree juice is not essential, but 

 that we have a substitute for it in the spurge or wartwort, which yields a 

 milky juice applicable for the purpose. Kalsamine is tempera with a con- 

 servative surface ; but neither of them are so durable under the operation of 

 the atmosphere as fresco and encaustic. 



Mr. Latilla mentions a curious circumstance with regard to fresco, that in 

 the course of drying it frequently exhibits an alarming appearance, the colour 

 looking patchy and faint, and a white mould rising to the surface. In the 

 course of two or three months, various changes succeed each other till the 

 picture almost entirely disappears ; but as the plaster dries, it shows itself 

 with more tha;i pristine beauty. Michael Angelo was so troubled with this 

 phenomenon while painting the Sistine Chapel, that he was about in disgust 

 to throw up the work, until he was assured by Julian da San Gallo of the 

 temporary nature of this operation, and the causes of it. 



A great many experiments are now being made as to the best materials for 

 cement ; and we understand that Mr. Alfred Francis, in the course of a long 

 investigation on this subject, has even succeeded in getting mural painting to 

 withstand the operation of the atmosphere. The subject is important, and 

 we hope the residts of these experiments will be communicated to the public. 



A Manual of the Steam Engine. Cy RiCH.\Ea D. Hoblvx, A.M., Oxon. 

 Loudon : Webster and Gear>', 1812. 



We should be glad to know for what class of readers Mr. Hohlyn's book 

 is designed. The professional engineer can hardly be supposed to be edified 

 by an omnium ijatJienmi of the most trite and superficial remarks on steam of 

 the last half century, and the general reader has nothing further to desire 

 after the admirable popular treatise on the steam engine by Dr. Lardner. 

 There is no redeeming quality about Mr. Hoblyn's book. He does not treat 

 of any new branch of inquiry connected with the steam engine, nor of any 

 new application of steam power. He has adduced no new facts, suppMed no 

 new investigations ; he has neither shortened nor simplified any pre-existing 

 analysis, nor stated more felicitously the nature of any particular movement, 

 agency, or combination. The only thing he has succeeded in showing is, 

 that a man may set up for an instructor without any tolerable acquaintance 

 with the subject he professes to teach. A popular treatise upon the steam 

 engine is a complete superfluity, unless its merits be transcendant. Medio- 

 crity is unpardonable where great excellence has already been attained ; and 

 Dr. Lardner's treatise is a standard which it is fatal to come short of, and 

 hardly possible to surpass. 



An Account of Patent and other Methods of Preventing or Conmming 

 Smoke, lyc. By William West, Professional Chemist, Leeds. 



This pamphlet is a collection of various schemes for consuming or pre- 

 venting smoke, as promulgated by the several projectors at a pubhc meeting 

 held at Leeds in January last. It is difticult from such a heterogenous mass 

 of materials to analyse them without entering into the merits or demerits of 

 each, which would occupy the whole of our Journal for the next three 

 nioatlis, we therefore refer our readers to Mr. West's pamphlet, and let them 

 judge for tliemselves; however, we cannot allow this notice to pass without 

 observing that too much praise caunot be awarded to Mr. Eddison, the 

 spirited individual who called the meeting together, and who has devoted so 

 much of his valuable time and labour to an investigation of the subject. It 

 does not appear that the committee who met to consider of the several plans 

 submitted, or Mr. West, the compiler of the pamphlet before us, have come 

 to any determination as to which of the various plans is the best, and have, 

 like ourselves left it to the public to form their own opinion. 



Ilriphl „J Paris ahme the Level of the Ocean.— U appears, from geodetical 

 operations and direct levelling, that the zero of the hydromelic scale at the 

 Punt de Tournelle is 26-25 metres above the mean level of the ocean. 



THE ATMOSPHERIC RAILWAY. 



Sir — I am of opinion that the annexed passages, taken from the report to 

 the Committee of Privy Council on Atmospheric Railnays, by Col. Sir Frede- 

 rick Smith, R.E.,and Professor Barlow ought to be placed together to enable 

 the public to appreciate the value of one of the conclusions given at page 6 

 line I of their report. 



" Secondly, the cxpence of the formation of the line in cuttings, embank- 

 ments, bridges, tunnels and rails, will be very little less than for equal 

 lengths of railway to be worked by locomotive engines ; but the total cost of 

 the works will be much greater, owing to the expence of providing and 

 laying the atmospheric tube and erecting stationary engines." 



The latter part of the conclusion refers to Sanuida's estimate of £4000 

 for single and £7000 for a double line for the atmospheric apparatus for 

 impelling the trains ; but the question whether a less expensive line might 

 not be formed by means of steejier gradients, worked by a proportional 

 vacuum, appears to be dependent on tlie working force of different vacuums, 

 and it ought to he decided by the ratio of the increased cost of higher vacu- 

 ums in comparison with the increased resistance of higher gradients, 



and this subject is adverted to at pape 4 line 11 of the report. 



" In the pamphlets circulated by the patentees," credit is taken " for two 



important items, which we cannot altogether admit. " Another 



questionable item is the reduced expence of cuttings and embankments, it 

 being assumed by the patentees that not having to take the locomotive up a 

 plane, much steeper gradients may be introduced than in present lines ; that 

 a great part of the power of a heavy locomotive is expended in overcoming 

 its own gravity and resistance in ascending steep planes is certainly true ; 

 and it is equally true that on the atmospheric principle the whole additional 

 force is exerted on the load itself. This is unquestionably an advantage, but. 

 stiU v.e think its importance has been greatly overrated." 



At the bottom of page J the commissioners remark, " Having stated our 

 own views, and having given in the appendix the experimental results and 

 investigations on which they are founded." On referring to the appendix I 

 find they state at page 11, line I, " We were desu-ous, if possible, to ascer- 

 tain the working force which different vacuums possessed of urging a train' 

 forward, but we failed of obtaining on this part of our inquiry any useful 

 results, the engine not having sufficient power to preserve the vacuums 

 constant." 



The details of four experiments are then inserted, and it is added, " No 

 conclusions can be drawn from these four experiments except that by the 

 falling of the mercury, it is clear that with all the force thrown upon the 

 engine, it was inadequate to the duty it had to perform." 



I apprehend the case made out by the Report respecting a reduction of 

 expence in the formation of the line itself, for an atmospheric railway, stands 

 thus : — 1st, the commissioners think the patentees have overrated the advan- 

 tage that may be derived from the introduction of steeper gradients or por- 

 tions of the line to be worked by a higher than average vacuum otherwise 

 employed, and in the consequent reduction of the cost of the line. 2nd, 

 that they admit the additional force of such increased vacuum is expended 

 on the load itself. 3rd, that in consequence of the inability of the engine 

 to presen'e a constant vacuum, they were unable to obtain data for the 

 determination of the limits within which the steeper gradients suggested by 

 the patentees could be rendered available with the higher vacuums, or under 

 what conditions the larger tube also suggested by the patentees for a low 

 vacuum would be required on steeper gradients. 4th, that their conclusion, 

 that a very small reduction of the expence of the formation of the line itself 

 can be effected, is not founded on any evidence as yet submitted to the pub- 

 lic, but rests on their own opinions. Time and trial must decide on the 

 respective values of the assertions of the patentees and the thoughts of the 

 commissioners. A jury, by the usage of this country, is directed to give the 

 prisoner the benefit of a doubt. Commissioners, acting on different princi- 

 ples, report against an inventor. 



REGUL.\TION OF CHIMNEYS. 



Sir — On reading over the Act for the future regulation of Chimnies, with 

 a view clearly to understand its intention, but which is not very easy, my 

 attention was arrested by the observation "or of greater length than four 

 feet OUT OF the ivall ; " and I have in vain tried to decide in my own mind 

 what our legislators mean by it, as the flue must of necessity (as far as I can 

 understand) be in the wall ; and why a less length than four feet should be 

 exempt from the rule as to the size of the flue. Perhajis you, Sir, or some 

 of your readers, will be good enough to remark on this in your next. 



I have not heard whether the Architect's Institute have yet acted on your 

 suggestion of September last. 



I am. Sir, 



Your obedient servant, 



March 24. A Subscriber. 



[It appears to us that why the length of 4 ft. out of the wall is exempted, 

 is to give an opportunity of introducing chimney shafts and pots with a con- 

 traded opening. — Editor.] 



