July 7, 1898] 



NATURE 



237 



the surface. The process by which this colouring is effected 

 has long been employed, and is thus described in an old receipt. 

 Apply with a brush to the surface of the medal common crocus 

 powder, jewellers' rouge, previously made into a smooth paste 

 with water. When dry, expose the medal over a clear fire for 

 about one minute ; lastly, when the medal is sufficiently cold, 

 polish it with a plate brush. The exact composition of the 

 superficial layer of oxide which is formed, has, I believe, never 

 been ascertained ; but it is well known that the tint varies greatly 

 from light brown to deep chocolate, according to the particular 

 variety of -oxide of iron which is used. 



With a view to ascertain whether this old method could not 

 be replaced with advantage, it was natural to turn to the work 

 of Japanese artists, who are masters in the art of giving pro- 

 tective surfaces of varied tints either to copper in its pure state 

 or to copper alloys. I have shown elsewhere ' that in conduct- 

 ing such operations the Japanese employ dilute boiling solutions 

 of certain salts of which verdigris and sulphate of copper are the 

 more important. 



The following solution ^ has been found to answer fairly well, 

 even when the ordinary European verdigris, which is a basic 

 acetate of copper, is employed : — 



Verdigris 87 grains 



Sulphate of copper 437 ,, 



Nitre 87 ,, 



Common salt 68 ,, 



Sulphur ... 233 ,, 



Water l gallon 



In Japan, however, *' verdigris" is made by the action of 

 plum-juice vinegar on plates of copper which contain certain 

 metallic impurities. Such native verdigris has consequently a 

 very complex constitution. It is called " Rokusho," and cannot 

 be procured in this country ; but I am indebted for a sample of 

 it to Mr. W. Gowland, formerly technical adviser to the 

 Japanese Mint at Osaka. He obtained it from a famous maker 

 of verdigris at Osaka, who persistently refused to give any 

 information respecting its mode of manufacture. Mr. Gowland 

 also gave me an elaborate description of the method of employ- 

 ing this verdigris in the colouring of copper medals, a method 

 which has only been adopted in Japan as the result of a long 

 series of experiments. Guided by an analysis which was made 

 of this " Rokusho," a mixture was compounded which produced 

 (juite as fine patina on copper as the native " Rokusho," though 

 its action was less certain and less rapid. The series of tints 

 which may be obtained by slight variations in the composition 

 of the " Rokusho " is truly remarkable. These tints range from 

 golden yellow through deep brown to bright red, the colour 

 mainly depending on the relative amounts of malate, urate, and 

 chloride of sodium which are present. 



The quality of the copper also exerts a very great influence 

 on the tint of the patina ; the difference, for instance, between 

 ordinary "best select" copper of the smelter and "electro" 

 copper, is very marked, as the former becomes dark brown and 

 the latter golden yellow when boiled in the same solution of 

 " Rokusho." Since the close of the year 1897, over 50CX) 

 medals have been treated by the method which has just been 

 described. Apart from the mere tint of the medal, the Japanese 

 artists attach much importance to producing a sheen or 

 damascening which shows through a transparent patina. This 

 is effected by developing the crystalline texture of the copper by 

 a preliminary treatment of the medal before it is boiled in 

 the solution of " Rokusho." 



In France, medals of true bronze containing much zinc are 

 -truck, and although the colour is heightened by superficial 

 oxidation, produced by gentle heating, no true patination is 

 effected. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 

 By the will of the late Mr. Edward O. Bleackley, the Owens 

 College, Manchester, receives 500/. for "Bleackley Scholar- 

 ships." 



We have more than once in the.se columns called attention to 

 the views expressed by Prof. Meldola and others concerning the 



J A paper " On the Use of Alloys in Art Metal-work." (Jourruti of the 

 Society of Arts, June 13, 1890.) 



2 A similar solution for heightening the colour of gilded metals is 

 described by Benvenuto Cellini in his " Trattato dell' Oroficeria in Fiorenza, 

 1568." 



NO. 1497, VOL. 58] 



futility of occasional instruction in miscellaneous subjects as 

 carried on at great cost to the county by many Technical 

 Instruction Committees, more particularly in rural districts. 

 An advocate of these views has now been found in the person 

 of the Countess of Warwick, who, acting on the advice of Prof. 

 Meldola, has established a small school of science at Bigods, 

 near Dunmow in Essex, on her own estate. The school at 

 present contains about sixty pupils of both sexes, and by way of 

 a beginning it is proposed to select twenty of the most highly 

 qualified for instruction under the " School of Science " curricu- 

 lum of the Science and Art Department. Lady Warwick 

 deserves every encouragement in this praiseworthy effort to 

 bring systematic instruction within the reach of a class of the 

 community more in need of such assistance even than the 

 inhabitants of large towns, and we learn that the Essex County 

 Council has wisely determined to co-operate in the movement. 

 The experiment is one in every way deserving of success, and 

 the results will be watched with interest all over the country.. 

 One of the weakest points in modern technical education^ 

 schemes has been the lack of such institutions in the thinly- 

 populated agricultural districts, and the county of Essex has 

 done well in taking part in an experiment which cannot 

 but lead to results of the greatest importance. Mr. E. E. 

 Hennesey, of the Royal College of Science, has been ap- 

 pointed principal of the school, which is provided with, 

 laboratories, lecture and class rooms, a workshop and laundry, . 

 garden plots, &c., and is situated in a most pleasant and 

 secluded corner of the county, about a mile and a half from 

 Dunmow railway station. The mansion adjoining the schooL 

 has been handed over by the Countess for the use of the staff 

 and of boarders, and the neighbouring farm is available for field 

 demonstrations. 



SCIENTIFIC SERIAL. 



Symons's Monthly Meteorological Magazine, June. — Lightning 

 conductors, by A. W^ Preston. — The author refers to a theory 

 put forth by some architects that old churches which have never 

 been struck by lightning do not require conductors, as the 

 probability is they never will be struck. The editor of the 

 Magazine will be glad to receive any evidence upon the subject, 

 — Results of meteorological observations at Camden Square,. 

 London, for forty years. These show that the mean of all the 

 highest readings was 78°!, and of all the lowest 33° "8 ; the 

 average rainfall is f92 inches, against 2*26 inches in the 

 present year. — Summer rainfall, by A. B. MacDowall. Based 

 upon the rainfall at Greenwich Observatory since 1841, the 

 author finds { i ) that in the first five years after sunspot minimunn 

 years, there have always been more dry summers than wet, and 

 (2) that in each group of five consecutive years ending with a 

 sunspot minimum year, there have been (with one exception) ■ 

 more wet summers than dry. These facts point to a tendency 

 for a wet summer this year. — This number contains a long, if 

 not unique, well record, containing the approximate height (ins 

 feet above Ordnance datum) of the top of the water in Mr. L. 

 Wood's well at Chilgrove, near Chichester, since 1836. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, June 9. — "On the Heat dissipated by a 

 Platinum Surface at High Temperatures." By J. E. Petavel, 

 1 85 1 Exhibition Scholar. Communicated by Lord Rayleigh» 

 F.R.S. 



The first part of the paper refers to the emissivity of a bright 

 platinum surface in air, hydrogen, carbon dioxide, and in othej 

 gases. 



In the case of each of the above gases the values of the- 

 emissivity are given at three distinct pressures ; namely, 6, 76- 

 and 228 centimetres of mercury. 



The temperature measurements are based on the researches of 

 Callendar and Griffiths, confirmed by the recent determinations, 

 of Heycock and Neville. To check the calibration of the 

 thermometers at higher temperatures, the melting point of 

 palladium was used. In all cases observations were made from 

 a temperature of 100° C. to temperature of 1200° C, and a 

 number of the curves are extended to 1779° C. by a direct 



