Howe, Herbert A. (Herbert Alonzo), 1858-1926 · Meadville, Penna., Flood and Vincent · leaf 142
h is placed between the tool andthe glass. A better material is obtained by driving ablast of air into melted iron. A cloud of minuteparticles of iron is blown out; being chilled by contactwith the air they settle down as a very fine powder. After the lens has been brought nearly to the propershape… … Fig. 70.—Machine for Polishing Lenses. The grinding. The polishing. 136 A Study of the Sky. The testing. An artificialstar. of pitch, instead of squares of cast-iron. The lens lieson a table which turns slowly. The tool is moved bytwo wooden rods, each of which is driven by a crank atits further…
Astronomy
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![An illustration from Novo teatro di machine et edificii per uarie et sicure operationi : co[n] le loro figure tagliate in rame é la dichiaratione, e dimostratione di ciascuna : opera necesaria ad architetti, e a quelli, ch[e] di tale studio si dilettano (1607)](https://img.insideoutlibrary.com/img/200/ia-novoteatrodimach00zonc-63-38.webp)
