Historical judgment must rest on the recognition of fundamental relationships in space as well as in time, and these are often made intelligible through the medium of maps. Introduction to Charles Paullin, Atlas of the Historical Geography of the United Slates (Washington, 1932), xi. Compared with the wealth of material on both other aspects of historiography and cartographic history, historical atlases are relatively neglected, and rarely considered as a genre. 1 Some of the leading historians of the last fifty years have been associated with the compilation of historical atlases and they still enjoy substantial sales, but there has been little discussion of their development, value and pitfalls. Yet historical atlases * I would like to thank the Research and Initiatives Committee of Durham University for granting me a ' mid-career award' to work on historical atlases, and

Astronauts traveling beyond low Earth orbit will be exposed to galactic cosmic radiation (GCR); understanding how high energy ionizing radiation modifies the bone response to mechanical unloading is important to assuring crew health. To investigate this, we exposed 4-mo-old female Balb/cBYJ mice to an acute space-relevant dose of 0.5 Gy 56 Fe or sham ( n = ~8/group); 4 days later, half of the mice were also subjected to a ground-based analog for 1/6 g (partial weightbearing) (G/6) for 21 days. Microcomputed tomography (µ-CT) of the distal femur reveals that 56 Fe exposure resulted in 65–78% greater volume and improved microarchitecture of cancellous bone after 21 d compared to sham controls. Radiation also leads to significant increases in three measures of energy absorption at the mid-shaft femur and an increase in stiffness of the L4 vertebra. No significant effects of radiation on bone formation indices are detected; however, G/6 leads to reduced % mineralizing surface on the inner mid-tibial bone surface. In separate groups allowed 21 days of weightbearing recovery from G/6 and/or 56 Fe exposure, radiation-exposed mice still exhibit greater bone mass and improved microarchitecture vs. sham control. However, femoral bone energy absorption values are no longer higher in the 56 Fe-exposed WB mice vs. sham controls. We provide evidence for persistent positive impacts of high-LET radiation exposure preceding a period of full or partial weightbearing on bone mass and microarchitecture in the distal femur and, for full weightbearing mice only and more transiently, cortical bone energy absorption values.

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