20 Of the AttraSlion of Cohesion.

"Planes , and Cryjlal Buttons: The Ascentof Water between Glass Planes , and in Ca-pillary Pub es: The rising of Water by the

Sides

common leaden Bullets will adhere so firmly together,as to require upwards of 80 Ib. to separate them,

2. In polifh’d Surfaces that are very hard, as Glass,Brass, &c, it is impossible to bring them into such closeContact as to cohere without the Interposition of Water,or something humid, to fill the Pores by expelling theAir contained therein, which prevents the Planes com-ing together while dry; the Humidity in this Cafe provesa Cement which holds the Planes together by all itsForce of Attraction on either Side,

3. This Force of Attraction between the Brass Planesis greater with Oil than with Water ; and greater withany Sort of Grease or Fat that will harden with Coldthan with Ois I never yet could meet with four Meirstrong enough to separate Planes thus put together,which are but 4' Inches Diameter ; and therefore theycohere with a Force much superior to the Force or Pres-sure of Air on such a Surface, which contains about 14square Inches, and allowing 15 Ib. for Pressure to everyInch, it will amount to but 210 Ib. which is not halfthe Strength of four Men palling against each other tothe best Advantage. I have often seen six Men en-deavour to separate them in vain.

4. Professor Muschenbroek has made many Experi-ments to shew the Force of "Cohesion between Planesof various Substances, and about 2 Inches Diameter,well polished, having first heated them in boiling Wa-ter, and then besmeared them first with a cold Tallow-Candle, and afterwards with boiling Grease, and theWeights to separate them were as

in

Table ;Planes

the following

Cold Grease.

Hot Grease.Ib ,

Glass — 130 Ib.

3 00

Brass — 150

800

Copper — 200

850

Marble — 225

600

Silver — 150

250

Iron — 300

950

5. These