Proceedings of the Polttecexic Associatiox. 867 



The chairman spoke strongly in favor of this apparatus ; he thought 

 there was no objections to placing all possible^ safeguards around the 

 boiler, and that the owners of boilers should have in their possession 

 the evidence as to the pressure in the boiler during the whole work 

 of the engine, which these diagrams will furnish. 



Mr. K^ormon "Wiard said he had never seen a boiler that exploded 

 whicli was stretched in the weakest pawt. He had invariably 

 found boilers to burst in the strongest part. He had been riding on 

 locomotives for the last nine months. 



Mr. C E. Emery remarked that this system of recording the opera- 

 tion of an engine was used by Mr. Allen in the Collins steamers when 

 .they tirst started. What is much wanted is a machine that will 

 measure the duty of an engine constantly. 



Death of Dr. W. Eqwell. 



Dr. D. D. Parmelee offered a resolution in relation to the death of 

 Dr. Warren Rowell, an active member of the Polytechnic Association. 



The resolution was seconded by Dr. Feuchtwanger, who said that 

 Dr. Rowell was a man of no ordinary talents as an inventor. In his 

 o"\vn profession he succeeded in restoring speech to a lady who had 

 lost her palate, by making a gold one. 



After some remarks from the chairman on the character and worth 

 of the deceased, the resolution was carried unanimously^ 



The following paper was then read : 



PLUMBAGO. 



Dr. Lewis Feuclitwanger. — Among the most refractory substances 

 in nature is the mineral plumbago, which is called black lead, graphite, 

 and carburet of iron. Its name, plumbago, is derived from the Latin 

 ^'■plumhum ago^^ meaning, " I act like lead ; " as metallic lead was, 

 up to the fifteenth century, used for drawing on paper ; the name 

 black lead has the same origin ; graphite is from a Greek word, mean- 

 ing " I write ; " the name carburet of iron is more appropriate, as the 

 mineral consists of ninetj' odd per cent of carbon and a fair per cent 

 of iron. The Brazilian plumbago, however, is pure carbon. All the 

 names just mentioned are used in daily life. 



It is quite soft, has a specific gravity of 2.09, a metallic lustre, a 

 shining streak, and an iron-black to steel-gray color. It is opaque, 

 soils paper and feels greasy. When of laminated structure, its laminse 

 are flexible ; but it also occurs massive and granular. Its regular 

 crystal form is a rhombohedron, but hexagonal tabular crystals are 



