488 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



necticut, that to avoid this bending and jarring at the ends of the rails, 

 they placed the end of the rail a little above the one that followed it. 



Mr, Bull read an extract from a Boston paper, giving an account of the 

 diameters of the telescopes in the various observatories. 



The largest object glasses hitherto made for a telescope are those of the 

 observatories at Pulkova, in Russia, and at Cambridge, in Massachusetts, 

 These have an aperture of something less than sixteen inches, and a focus 

 of twenty-one feet, but the available apertures are considerably less. The 

 observatories at Ann Arbor, Michigan, and Cincinnati, have telescopes 

 whose apertures are only twelve and a half and twelve and three-quarter 

 inches. That of the National Observatory, in Washington, has only nine 

 and a half inches. Mr. Alvan Clark, of Boston, long known as one of the 

 best makers in the world, has succeeded in making a glass which gives an 

 available aperture of eighteen inches and a half. 



The Chairman said that Prof. Draper, of the New York University, has 

 made a telescopic reflector of silvered glass, which was considered a suc- 

 cess. The usual mode is to make them of metal. It was at his residence at 

 Hastings. 



Mr. Parmelee said he deemed it proper to call attention to an article 

 that was now manufacturing to a very large extent for the purpose of being 

 sent to the army during the summer, and that was a new beer cooler. The 

 point to which he wished to call attention w^as the use of lead pipes, with- 

 out being tinned on the inside. Now, it is evident to any one at all 

 acquainted with the subject, that the use of lead pipe for this purpose was 

 calculated to produce injurious effects. The use of lead pipes for liquids, 

 such as beer, was very reprehensible. The excuse for not using tinned 

 pipes was that there was no danger, as the pipes were washed out every 

 day. The cooling is done in the usual way, by the beer passing through 

 coils of this pipe. They are got up in very neat style, silver mounted and 

 well made throughout. 



Mr. Rowell, in answer to some inquiries at the last meeting, drew a dia- 

 gram on the blackboard, to illustrate experiments made at the Metropoli- 

 tan Mills to test the utility of the cut off in steam engines. An engine, the 

 cylinder of which was fourteen inches diameter; a sleeve or inside cylin- 

 der was made to fit into this, so that it was reduced to half its former area 

 of piston, and both engines were tried successively; with the fourteen inch 

 cjdindcr the steam was u^ed with the cut off. or expansively, but when used 

 with the inside cylinder there was no cut ofi' used, but the steam was used 

 to end of the stroke; and after repeated experiments, the preference was 

 given to the small cylinder, using steam to the end. 



The Chairman said that Mr. Roweil's argument favored the use of small 

 cylinders, when it was well known that the friction of a piston increased as 

 diameter, and the pressure increased as the square of the diameter. The 

 use of large cjdinders would, therefore, relatively decrease the friction. 



The subject of " Rock Oil" was resumed. 



Prof. Everett said that Oil creek was 135 miles above Pittsburg, and 

 was navigated part of the year by steamboats, and at other times the up- 

 per part was navigable by flat boats. The oil was first obtained by boring 

 from two to three hundred feet, but he had seen one well that was found at 



