2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/153214We study pattern selection of cracks in directionally drying fractures by analyzing the experimental systems recently devised by C. Allain and L. Limat. [Phys. Rev. Lett. {\bf 74}, 2981 (1995).] Proposing a simple picture of crack formation, we clarify the mechanism of how cracks array regularly and find that the interval between neighboring cracks is proportional to the $2/3$ power of the cell thickness. This result explains well the experimental data of Allain and Limat.12 pages, REVTeX with 3 figures (uuencoded tar-compressed postscript)Pattern Formation and Solitonstext