CONTENTS. XI 



IV. THE CONSTANT ERROR OF THE MEAN: 



Constant Error of Coins, 20. Lower and Higher 

 Limit, 21. Laboratory Work Alone not Enough, 21. 

 Observatory Work Alone not Enough, 22. What Ails 

 the Mean, 22. Constant Errors Large, 23. 



V. ACTUAL ERRORS OF THE MEAN: 



Mallet's Determinations of the Atomic Weight of 

 Gold, 24. The Seven Means are all Mean, 25. Our 

 Little Diagram Shows the Facts, 26. Mallet did not 

 Hit the Mark, 26. If we don't Know the Tenth, we 

 don't Know the Thousandth, 27. Mallet Suffers from 

 Morbus Stasii, 27. Our Conclusion, 28. 



VI. ERRORS IN PRECISION: 



The Common Practice, 28. The Two Fatal Com- 

 mon Errors, 29. Don't Give us Your Fancy for Fact, 

 29. Edgar F. Smith and W. L. Hardin, 30-32. 



VII. ERRORS DUE TO FALSE DATA: 



Adopting Data, 32. Ramsay and Aston, 33. H. 

 Moissan and H. Gautier, 34. Armand Gautier and J. 

 Aloy, 35. My Method in the Comptes Rendus, 37. 



VIII. ERRORS OF WEIGHING : 



Weighing First and Last, 38. Dumas' Combustion 

 of the Diamond, 39. Precision of Weighing, 40. The 

 Balance used by Dumas, 40. The Balance used by Ber- 

 zelius, 41. Our Fine Balances, 41. Weighing the 

 Weighers, 42. Great Chemist, Poor Balance, 43. The 

 Man and the Balance, 44. Official Rule, 44. True and 

 Sham Accuracy, 45. The Number of Decimals, 45. A 

 Fine Probable Error, 46. 



IX. MINUTE CHEMICAL ERRORS: 



Chemical Processes, 46. Our Standard of Matter, 

 48. Oxidation of Metals, 49. Dry Way Processes and 

 Crystals, 49-51. 



X. LARGER CHEMICAL ERRORS: 



Purification by Distillation, 51. Good Special 

 Methods, 52. Methods Giving Varying Results, 53. 

 False Methods, 54. Louis Henry of Louvain, 56-57. 



