320 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



the black-board the form of the rhizapod, and proceeded to say that 'this 

 animal is found in many of our waters. The fossil is found in tiie palaeozoic 

 rocks on tlie Mississippi, and is as large as one foot in diameter. In the 

 tertiary formation of the valley of the Nile, and at Thebes, it sometimes 

 attains the size of a twenty-live cent piece. But the rhizapods of the 

 primitive rock formations are from two to three feet in diameter. He had 

 seen them of that size. It is the law of the lower animal kingdom that 

 they begin life, at the minimum points, both as to size and as to number; 

 that they go on increasing in successive ages until they arrive at their 

 maximum Having attained their greatest extent all over the world, they 

 begin to decrease, and ultimately disappear from among the animals known 

 to man. This is the case with the rhizapods, which are now a mere micros- 

 copical infusoria; and, in following out this general law, we are carried 

 back in our imagination to that period in the earth's history, anterior to the 

 formation of rocks, when these animals were but a mere speck, and forward 

 to tlie time when they attained the size of those he had represented on the 

 black-board. 



The Best Mode of Using Steam Expansively. 



This question, discussed quite thoroughly not lo))g since, was again 

 brought up, mainly for the purpose of hearing Mr. J. Wyatt Reid, who took 

 the floor, and, with the aid of figures and diagrams, attempted to prove 

 that there was a great advantage gained bj' first using the steam at high 

 pressure in one cylinder, and using it again in a more expanded state in 

 another cylinder of greatly increased diameter. In conclusion, he stated 

 that he had presented these views to several practical engineers, and they 

 can present no valid objections to his views. 



The Chair observed that the plan of Mr Reid was that of Hornblower 

 and of Wolf, who first practically applied the principle of expansion about 

 the year 1782. 



Mr. D. Blanchard remarked that he failed to see the benefit of using two 

 cylinders when the whole gain by expansion could be secured in one cylin- 

 der by using a cut-off. When the cylinder is properly^ clothed with non- 

 conductors the cut-off may be very short. There was an engine running in 

 Waterbur}', Conn., in which the steam was cut off at one-eighth of the stroke, 

 — the piston being carried the other seven-eighths by the expansive power 

 of the steam which at first filled oidy one-eighth. 



Mr. John B. Root said the late Mr. Barrow, a well known inventor of 

 this city, had used a large and small cylinder, and the only benefit he had 

 found was that the stroke was more even throughout, but there was no 

 economy whatever. Mr. Root gave several instances where two cylinders 

 had been used, and aftcrv/ard one had been removed, and the remaining 

 one was found to do all the work which had been done by two previously. 



Mr. Watson alluded to several constructions which had lately been made 

 embracing this double cylinder idea, and the extravagant claims made re- 

 garding saving of fuel. 



Dr. W. Rowell gave the argument against short cut-off which has already 



been reported in the volume of transactions of the Institute. He concluded 



ng some novel experiments arc now being made in the Metropolitan 



