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The refraction and extinction in the Earth’s atmosphere depend on the atmosphere’s structure, so it was natural to try to infer that structure from optical observations. Efforts to extract structure from observed refractions led to proof that this is possible only below the astronomical horizon. Direct studies of the real atmosphere show complicated, variable structure. The complex history of relations between structure and refraction is outlined by citing some important works.

Gaspard Monge has received undue credit for his observations of mirages in 1798 in Egypt. He did not discover inferior mirages; they were known to sailors before 1687, and the term mirage had entered the French literature in 1753. Monge’s “total reflection” explanation for them was seriously flawed; it had already been considered and rejected by Gruber and by Büsch, and was promptly criticized by others. Yet he continues to be given credit for the first scientific explanation of mirages; and his false total-reflection mechanism survives today in some textbooks. Apparently this is due to its superficial simplicity, which appeals to novices.

ObjectiveThis study aimed to describe two cases of acute respiratory distress syndrome (ARDS) secondary to novel coronavirus disease 2019 (COVID-19) in pregnant women requiring extracorporeal membrane oxygenation (ECMO), and resulting in premature delivery.Study designThe clinical course of two women hospitalized with ARDS due to COVID-19 care in our intensive care (ICU) is summarized; both participants provided consent to be included in this case series.ResultsBoth women recovered with no clinical sequelae. Neonatal outcomes were within the realm of expected for prematurity with the exception of coagulopathy. There was no vertical transmission to the neonates.ConclusionThis case series highlights that ECMO is a feasible treatment in the pregnant woman with severe COVID-19 and that delivery can be performed safely on ECMO with no additional risk to the fetus. While ECMO carries its natural risks, it should be considered a viable option during pregnancy and the postpartum period.Key points· COVID-19 may present with a more severe course in pregnancy.. · ECMO may be used in pregnant woman with severe COVID-19.. · Delivery can be performed on ECMO without added fetal risk..