Mr, W. Crookes on the Discovery of the Metal Thallium. 61 



though these labels and their history, as given below*, might 

 not be worth much in a question of mere priority, I do not 

 doubt that they will be useful in regard to the question whether 

 the metallic nature of thallium was known to me before M. Lamy 

 came to London in June, or whether that knowledge was then 

 first obtained by me from M. Lamy. I may appeal to any 

 chemist to say whether these labels do not prove that the writer 

 had a perfect knowledge of the metallic nature of thallium at the 

 time the order for them was given to Messrs. Silverlock. 



I can also refer to the testimony of persons who saw metallic 

 thallium in my laboratory in January 1862, long before M. 

 Lamy appeared in the matter f. 



Thallium. 



Oxide of 

 Thallium. 



Sulphide of 

 Thallium. 



Basic Chloride 

 of Thallium. 



Iodide of 

 Thallium. 



Sulphate of 

 Thallium. 



Chloride of 

 Thallium. 



Nitrate of 

 Thallium. 



Ferrocvanide 

 of Thallium. 



Cyanide of 

 Thallium. 



Phosphate of 

 Thallium. 



Carbonate of 

 Thallium. 



Thallium 

 (OaXXos). 



Chromate of 

 Thallium. 



Thallium, 

 Sublimed. 



Oxalate of 

 Thallium. 



" Printing Office, 

 Wardrobe Terrace, Doctor's Commons, 

 London, 18th May, 1863. 

 "Sir, — In reply to your request, I beg to inform you that I have 

 examined the books of this firm, and find that 50 sheets of labels 

 (Thallium, Sulphate of Thallium, Nitrate of Thallium, &c.) were printed 

 here and delivered on or about April 25, 1862 ; the order having been 

 given a few days prior to that date. The original manuscript of the labels 

 is still in my possession. 



"I am, Sir, 



" Yours obediently, 



" Pro H. Silverlock, 

 "Mr. W. Crookes, 20 Mornington Road." "P. Perkins." 



t "5 New Cavendish Street, London, W., 



June 16, 1862. 



"My dear Sir, — I well remember paying you a visit in January last 

 to see the ' thallium* you had then got into a more definite shape. As I 

 had seen its reaction in the spectroscope many months before, and was 

 much interested in the remarkable discovery, I felt great pleasure in 

 watching the progress you had then made in the investigation. 

 _ "You had several compounds of the body, including, if I remember 

 rightly, the sulphide (of which I possess a specimen), and the oxide which 

 you had obtained in crystals. The quantity of material you had, however, 

 was but small ; and it was only by exercising the greatest amount of inge- 

 nuity that you were able to demonstrate the nature of its compounds. 



"The most interesting point, I well remember, was the metal itself, 

 deposited by means of a weak galvanic current, — first on a bar of copper, 



