46 REPORT — 1867. 



of clnoiuic oxido. In proof of tliis view, it may be stated that Mr. Swan has hitely 

 devised a mode of working, in which a minute quantity of chrome alum or sulphate 

 of chromium is used instead of the red chromate, and it is foimd that, when dried, 

 this mixture is not again atfected by water. The carbon prints of Mr. Swan, which 

 were exhibited last year at Nottingham, are illustrations of the use of a eliromate 

 in conjunction v,'ith gelatine and pigments. Mr. Woodbuiy's process is also based 

 on the insolubility of the chromo-gelatiue after exposm'e to light, and upon the 

 subsequent action of water upon a sensitive film, which has been in different degrees 

 influenced by insolation imder an ordinary photographic negative. The depths of 

 tint in the original are represented by variations m the thickness of the film of 

 gelatine left unacted upon by water, and this dried may then be used as a matrix 

 to produce a corresponding series of depressions upon a surface of lead or type- 

 metal by the aid of a powerful hydraidic press. The blocks so produced serve for 

 printing" off a great number of proofs when they are liberally '-inked" with warm 

 gelatine, highly charged with Frankfort black or other suitable pigment, and pressed 

 down upon"^a smooth sheet of paper until the excess of ink is forced out on all four 

 sides of the block and so removed from the space constituting the area of the pic- 

 ture, which, when set, is, lastly, protected with a varuisli of collodion. 



Mr. Woodbury has latelv perfected a modification of his process, which is ap- 

 plicable to the representation in high relief of microscopic objects. The method 

 consists in spreading a warm solution of gelatine, containing a little sugar and 

 bichromate of potash, over a glass plate previously coated with collodion. The 

 film sets on cooling, and is then placed in contact with an ordinary photographic 

 negative of the microscopic objects to be delineated, exposed to light, submitted as 

 before to the action of water, and the soluble portions washed away. "When the 

 surface moisture has evaporated, a mixture of plaster of Paris, containing a small 

 proportion of alum, is poiu-ed over the relief to the thickness of half an inch, and 

 left to set. When diy it will be found, owing to the alum in the plaster harden- 

 ing the surface of the gelatine directly on coming in contact there-w-ith, to leave the 

 gelatine easilv, vrithout any fear of adhesion. To give a finished appearance to 

 the resulting casts, this iutoglio, when dry, may be placed in a lathe, and a suit- 

 able border turned on it, which will bo 'represented in the residting proofs by a 

 raised border, similar to what is seen on medallions or plaster casts. The name of 

 the object may also be neatly engi-aved on the intaglio, to appear in raised cha- 

 racters on the reliefs. This intaglio should then be well waxed to fill up the pores, 

 and is ready for taking any number of impressions in plaster ; or a better plan is to 

 take one in plaster, and having smoothed away any defects, to moidd a reverse in 

 sulphur, which will give a gTcater number of fine impressions. The progi'ess made 

 during the year in perfecting the details of photolithogTaphy have led to the 

 practi'cal use" of this art as a means of procuring on a reduced scale printed repro- 

 ductions of the large series of lithographs issued for the use of the British army by 

 the Royal Carriage Department. The steps followed in conducting this process 

 were briefly described, and a variety of illustrations produced at a veiy low co.st 

 were exhilnted. The issue of these' photolithogi-aphs by the War Department has- 

 already attained to many thousands. 



Synthesis of Capro'ic Acid. By J. Alfeed Waxkltn and Eobeet Schexe. 



Mercuiy-amyl was prepared by the process of Frankland and Duppa, and con- 

 verted into zin'c-amyl by prolonged digestion with zinc. 



The puritj' of the mercuiy-amyl had been guaranteed by a determination of mer- 

 cury which agi'eed with the theoiy. 



The zinc-amyl was sealed up with sodium and heated in the water-bath. The 

 action of the sodium is very slow. Ha-^ing prepared sodium-amyl, we exposed it 

 to the action of dry carbonic acid, which acted energetically, evolving heat. The 

 product of the reaction was treated with water, evaporated down to diyness, and 

 the residue distilled with dilute sulphuric acid. An oily acid distilled over, and 

 was converted into a baryta salt. The baiyta salt was submitted to analysis, giving 

 results concordant -with the theoiy. Carbonic acid, therefore, behaves with sodiiim- 

 amvl iust as with sodiuui-cthyl and sodium-methvl, 



COo+NaC,Hii = C,Hi;Na02. 



