Coherence and Historical understanding in children's Biography and Historical Nonfiction Literature: A Content Analysis of Selected Orbis Pictus Books

The purpose of this study was to investigate a selection of children's historical nonfiction literature for evidence of coherence. Although research has been conducted on coherence of textbook material and its influences on comprehension there has been limited study on coherence in children's nonfiction literature. Generally, textual coherence has been seen as critical in the comprehensibility of content area textbooks because it concerns the unity of connections among ideas and information. Disciplinary coherence concerns the extent to which authors of historical text show readers how historians think and write. Since young readers are apprentices in learning historical content and conventions of historical thinking, evidence of disciplinary coherence is significant in nonfiction literature for young readers. The sample of the study contained 32 books published between 1989 and 2000 ranging in length from less than 90 pages to more than 150 pages. Content analysis was the quantitative research technique used to measure 84 variables of textual and disciplinary coherence in three passages of each book, as proportions of the total number of words for each book. Reliability analyses and an examination of 750 correlations showed the extent to which variables were related in the books. Three important findings emerged from the study that should be considered in the selection and use of children's historical nonfiction literature in classrooms. First, characteristics of coherence are significantly related together in high quality nonfiction literature. Second, shorter books have a higher proportion of textual coherence than longer books as measured in three passages. Third, presence of the author is related to characteristics of coherence throughout the books. The findings show that nonfiction literature offers students content that researchers have found textbooks lack. Both younger and older students have the opportunity to learn the conventions of historical thinking as they learn content through nonfiction literature. Further, the children's literature, represented in the Orbis Pictus list, shows students that authors select, interpret, and question information, and give other interpretations. The implications of the study for teaching history, teacher preparation in content and literacy, school practices, children's librarians, and publishers of children's nonfiction are discussed.

A 12,000 Year Record of Explosive Volcanism in the Siple Dome Ice Core, West Antarctica

Air mass trajectories in the Southern Hemisphere provide a mechanism for transport to and deposition of volcanic products on the Antarctic ice sheet from local volcanoes and from tropical and subtropical volcanic centers. This study extends the detailed record of Antarctic, South American, and equatorial volcanism over the last 12,000 years using continuous glaciochemical series developed from the Siple Dome A (SDMA) ice core, West Antarctica. The largest volcanic sulfate spike ( 280 mu g/L) occurs at 5881 B. C. E. Other large signals with unknown sources are observed around 325 B. C. E. ( 270 mu g/L) and 2818 B. C. E. ( 191 mu g/L). Ages of several large equatorial or Southern Hemisphere volcanic eruptions are synchronous with many sulfate peaks detected in the SDMA volcanic ice chemistry record. The microprobe "fingerprinting'' of glass shards in the SDMA core points to the following Antarctic volcanic centers as sources of tephra found in the SDMA core: Balenny Island, Pleiades, Mount Berlin, Mount Takahe, and Mount Melbourne as well as Mount Hudson and possibly Mount Burney volcanoes of South America. Identified volcanic sources provide an insight into the poorly resolved transport history of volcanic products from source volcanoes to the West Antarctic ice sheet.

New Data on Welshite, e.g. Ca2Mg3.8Mn0.62+Fe0.12+Sb1.55+O2 [Si2.8Be1.7Fe0.653+Al0.7As0.17O18], an Aenigmatite-Group Mineral

Electron and ion microprobe data on two samples of welshite from the type locality of Langban, Sweden, gave analytical totals of 99.38-99.57 wt.% and BeO contents of 4.82-5.11 wt.%, corresponding to 1.692-1.773 Be/20 O. Mossbauer and optical spectra of one of these samples gave Fe-[iv](3+)/Sigma Fe = 0.91, Fe-[iv](2+)/Sigma Fe = 0.09, and no evidence of Mn3+. The resulting formula for this sample is Ca2Mg3.8Mn0.62+Fe0.12+Sb1.55+O2[Si2.8Be1.7Fe0.653+Al0.7As0.17O18], and that for the second sample, Ca2Mg3.8Mn0.12+Fe0.12+F0.83+Sb1.25+O2[Si2.8Be1.8F0.653+Al0.25As0.25O18], is related by the substitution involving tetrahedral and octahedral sites: 0.59([vi,iv])(Fe,Al)(3+) approximate to 0.42([vi])(Mg,Mn,Fe)(2+) + 0.21(Sb-[vi],As-[iv])(5+), i.e. 3([vi,iv]) M3+ = 2([vi])M(2+) + M-[vi,iv](5+). WelShite is distinctive among aenigmatite-group minerals in the high proportion of Fe 3+ in tetrahedral coordination and is unique in its Be content, substantially exceeding 1Be per formula unit. Given the cation distributions in other minerals related to aenigmatite, we think it is reasonable to assume that at least one tetrahedral site is >50% occupied by Be and that one octahedral site is >50% occupied by Sb, so that welshite should be retained as a distinct species with its own name in the aenigmatite group.