On Two Occasions I Have Been Asked,

The Difference Between A Tool And A Machine Is Not Capable Of Very Precise Distinction; Nor Is It Necessary, In A Popular Explanation Of Those Terms, To Limit Very Strictly Their Acceptation.

To Those Who Have Chosen The Profession Of Medicine, A Knowledge Of Chemistry, And Of Some Branches Of Natural History, And, Indeed, Of Several Other Departments Of Science, Affords Useful Assistance.

A Tool Is Usually More Simple Than A Machine; It Is Generally Used With The Hand, Whilst A Machine Is Frequently Moved By Animal Or Steam Power.

Long Intervals Frequently Elapse Between The Discovery Of New Principles In Science And Their Practical Application... Those Intellectual Qualifications, Which Give Birth To New Principles Or To New Methods, Are Of Quite A Different Order From Those Which Are Necessary For Their Practical Application.

Mr. Herschel... Brought With Him The Calculations Of The Computers, And We Commenced The Tedious Process Of Verification. After A Time Many Discrepancies Occurred, And At One Point These Discordances Were So Numerous That I Exclaimed, "i Wish To God These Calculations Had Been Executed By Steam," To Which Herschel Replied, "it Is Quite Possible."