Abstract: This paper discusses the formula P_n=P₁/n² (q.v. printed in the textbook of Forest Measurement (P.16-18)published by Beijing Forest College, 1984)and points out that the above formula is incorrect. Its right formula according to author's opinion should be P_n=P₁/n². The author gives his reasons that the deviation of the calculated volume of a felled tree is decreased with increasing in the number of sections and is increased with increasing in the-taper of a stem(q.v, the equations (9), (11)).