\[ \begin{split} &\lim_{n \to \infty} n\left(\ln (n+1)-\ln n\right)=\\[16pt] &=\lim_{n \to \infty} n\left(\ln \frac{n+1}{n}\right)=\\[16pt] &=\lim_{n \to \infty} \ln \left(\frac{n+1}{n}\right)^n=\\[16pt] &=\lim_{n \to \infty} \ln \left(1+\frac{1}{n}\right)^n=\\[16pt] &=\lim_{n \to \infty} \ln e=1 \end{split} \]