W. Crookes on the Wax-paper Photographic Process. 165 



pans must be of glass, and the weights should consist of a set of 

 grain and a set of drachm weights. 



A sponge will be found useful for wiping up any of the solu- 

 tions that may have been spilt on the bench. Solid glass stirring 

 rods of about the thickness of a quill, and six or eight inches 

 long, and a small wedgewood pestle and mortar, are of great 

 service in many of the operations. 



Stoppered bottles should be employed for all the solutions; 

 and too much care cannot be taken to label each bottle accurately 

 and distinctly. 



19. Besides the above apparatus, the following materials and 

 chemicals are requisite. A rough estimate is also given of their 

 relative consumption in three months. 



Photographic paper, 270 sheets, or 112 square feet. 



Four pounds of wax. 



Three ounces of iodid of potassium 



Three ounces of bromid of potassium. 



Four ounces of nitrate of silver. 



Two ounces of glacial acetic acid. 



Four ounces of gallic acid. 



One pint of alcohol. 



Seven pounds of hyposulphite of soda. 



Half a pound of cyanid of potassium. 



Half a pint of concentrated nitric acid. 



Eighteen gallons of distilled water. 



20. The selection of a good sample of paper for the basis on 

 which the sensitive material is to be formed is of great import- 

 ance, as any imperfection will be a source of annoyance in every 

 stage of the process, and will hardly fail to show itself on the 

 finished picture. The paper, which from numerous experiments 

 I have found to be superior to any other, is that known as 

 Canson's thin photographic paper. This is manufactured with 

 great care, and is in general very uniform in quality. 



It will be found by far the most advantageous plan, when used 

 on a scale like the present, to order it of some wholesale sta- 

 tioner cut to the requisite dimensions. The size of the sheets 

 in use here is 4f inches by 12 f| inches*. Hitherto Messrs. 

 Hallifax and Co. 319, Oxford Street, have supplied us with the 

 paper of this size. 



21. I am indebted to Mr. Barclay of Eegent Street, wax 

 bleacher, for much valuable information concerning wax and its 

 adulterations, and for an extensive assortment of waxes of all 



* This is a most inconvenient size, as it involves the cutting of more than one 

 third of the paper to waste. The admirably ingenious arrangement of Mr. Ronnld's, 

 was not made with the view of employing Canson's pstper; or it would doubtless 

 have been contrived to accomodate sheets of a size which could be cut with less 

 waste, such as 4£ by 13 inches, or 4f by 11£ inches. 



