416 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



in; if it gains by cold the weights mnst be set farther out. To determine 

 this the chronometer is run in an oven at 100 to 120 degrees, and then 

 again in a refrigerator as low as possible, until the exact point is reached. 

 Chronometers are not often brought to true time, but after it is brought' 

 near, a record is kept of each day's variations, and when it goes to sea this 

 record or rate of variation goes with it to assist the mate in keeping his 

 reckoning. Capt. Oi*ouch, of the Creole, told me a few voj^ages since that 

 he came near losing his ship by being given a wrong rate with his chro- 

 nometer. I have at home a Willard clock that was made with a recoil 

 escapement; but a short time since I repaired it and put a dead-beat escape- 

 ment in. It keeps very good time, sometimes running months without any 

 perceptible variation. 



Dr. Rowell. — Mr. William Pardee made clocks sevei'al years ago of type 

 metal, or a composition of lead and zinc. The pinions were like the lan- 

 tern pinions. I had one running in my house for a year. He also made 

 cast-iron clocks with three wheels; the clock I had kept vei'y good time, 

 but the brass clock coming into use threw it out of the market. It was 

 said that Mr. Pardee was the inventor of the gimlet-pointed screw, but at 

 that time he could not get any one to assist him in introducing it. I recol- 

 lect in my boyhood of a cast-iron clock on the village church; it took up 

 the space of two feet square, and had but one hand and that was the hour 

 hand; it took two barrels of old cast iron to make it go, and a full half 

 hour to wind it, yet it served to tell the hour very well. 



Mr. Dibben. — I have a clock of the same make as the one Mr. Bradley 

 first exhibited, that keeps the very best of time. I have also a watch which 

 is considered a very fine one, and I find that the clock keeps far the best 

 time. I have access to watches that are deemed the very best, and that 

 are frequently timed and corrected by the sun, and comparing my clock 

 with them, I find it does not vary perceptibly for a long time. I will guar- 

 antee that it will not vary two seconds in a day, and this clock I bought 

 for one dollar and fifty cents. There is nothing remarkable about this, 

 there are no doubt hundreds of clocks that will do the same, only it requires 

 to be properly set and then regulated and regularly wound, for a great 

 deal depends on regular winding. 



India-Rubber Springs. 



A specimen of India-rubber car spring was presented for inspection that 

 had been in use four and a half years. 



Mr. Dibben. — Rubber spring has a greater durability than most people 

 imagine. I have known railroad companies to throw away rubber springs 

 when a little worn, and these to be bought up and brought to the factory, 

 put in a lathe and turned down, and then sold back again as new to the 

 railroad company. There is a great waste in this practice of throwing out 

 half-worn springs. 



Mathematical Instruments was selected as the subject for the next meet- 

 ing. Adjourned. 



