Three possible explanations for the mysterious crosses were considered. Firstly, they may have been miraculous and involved a direct intervention by God in the events of the world; secondly, angels or demons might have made use of natural forces in extraordinary ways; and thirdly, the laws of nature could provide a perfectly good explanation. In Kircher's view the ultimate cause of all things was divine will, but this was expressed, for the most part, through understandable natural laws; studying these laws therefore revealed the forces that lay beneath natural phenomena. The explanation for the cross-shaped marks, he concluded, was that fine ash and moisture had settled on cloth, taking cruciform shape defined by the weave itself. Kircher noted that the crosses had been seen on linen cloth but not on garments of wool, and that they had appeared only under certain specific conditions of temperature and moisture, causing "guttulae nitrosae" (nitrous drops) to form on the surface. To support his conclusion Kircher noted two instances of similar phenomena; when a tomcat had sprayed linen in the laundry room at the Jesuit College in Rome, the effect produced was yellow crosses following the weave of the cloth; the same had also been observed in the bed-linen of an elderly Jesuit who had accidentally wet his bed. He maintained however that an explanation through the operation of natural laws did not mean that the phenomenon did not contain an important divine message: "[Portents are] like hieroglyphic symbols swathed in enigmatic and allegorical meanings which the Divine Wisdom records in Heaven, Earth, and the elements as if in a hook and sets it before mortals to read; when they withdraw from the paths of Divine Will they are terrified by the threats held out before them, and turn back toward better fruits. Critical reception Like all of Kircher's work, Diatribe had to be submitted to the censors of the Jesuit order before it could be published. They did not block it, but informed Kircher that this was not the quality of work the order was expecting its scholars to produce. They noted that crosses had been found on meat and fruit as well as linen. Furthermore crosses were still continuing to appear, after the eruption had stopped and after the Sun had moved out of Leo. If they waited until the autumn rains washed the remaining ash out of the air, they would