(1)Developments in two materials--iron and concrete--formed the technological basis for much modern architecture. In 1779 English architect Thomas Pritchard designed the first structure built entirely of cast iron: Ironbridge, a bridge over the River Severn in England. At around the same time, another Englishman experimented with a compound of lime, clay, sand, and iron slag (矿渣) to produce concrete. Iron had been used since ancient time to tie building elements together, but after the construction of Ironbridge it took on a new role as a primary structural material. (2)Builders throughout Europe and North America began to set up houses with beams of iron instead of wood.
(3)One of the most spectacular examples of early iron construction was the Crystal Palace in London, England. Spreading over 18 acres, the building consisted entirely of screens of glass set within iron frames. Paxton adapted two major features of the architecture of the Crystal Pala
(1)Developments in two materials--iron and concrete--formed the technological basis for much modern architecture. In 1779 English architect Thomas Pritchard designed the first structure built entirely of cast iron: Ironbridge, a bridge over the River Severn in England. At around the same time, another Englishman experimented with a compound of lime, clay, sand, and iron slag (矿渣) to produce concrete. Iron had been used since ancient time to tie building elements together, but after the construction of Ironbridge it took on a new role as a primary structural material. (2)Builders throughout Europe and North America began to set up houses with beams of iron instead of wood.
(3)One of the most spectacular examples of early iron construction was the Crystal Palace in London, England. Spreading over 18 acres, the building consisted entirely of screens of glass set within iron frames. Paxton adapted two major features of the architecture of the Crystal Pala
(71)Developments in two materials--iron and concrete--formed the technological basis for much modern architecture. In 1779 English architect Thomas Pritchard designed the first structure built entirely of cast iron: Ironbridge, a bridge over the River Severn in England. At around the same time, another Englishman experimented with a compound of lime, clay, sand, and iron slag (矿渣) to produce concrete. Iron had been used since ancient time to tie building elements together, but after the construction of Ironbridge it took on a new role as a primary structural material. (72)Builders throughout Europe and North America began to set up houses with beams of iron instead of wood.
(73)One of the most spectacular examples of early iron construction was the Crystal Palace in London, England. Spreading over 18 acres, the building consisted entirely of screens of glass set within iron frames. Paxton adapted two major features of the architecture of the Crystal P
(1)Developments in two materials--iron and concrete--formed the technological basis for much modern architecture. In 1779 English architect Thomas Pritchard designed the first structure built entirely of cast iron: Ironbridge, a bridge over the River Severn in England. At around the same time, another Englishman experimented with a compound of lime, clay, sand, and iron slag (矿渣) to produce concrete. Iron had been used since ancient time to tie building elements together, but after the construction of Ironbridge it took on a new role as a primary structural material. (2)Builders throughout Europe and North America began to set up houses with beams of iron instead of wood.
(3)One of the most spectacular examples of early iron construction was the Crystal Palace in London, England. Spreading over 18 acres, the building consisted entirely of screens of glass set within iron frames. Paxton adapted two major features of the architecture of the Crysta
One of the most important social developments that helped to make possible a shift in thinking about the r01e of public education was the effect of the baby boom of the 1950s and 1960s on the schools. In the 1920s, but especially in the Depression conditions of the 1930s, the United States experienced a declining birth rate—every thousand women aged fifteen to forty-four gave birth to about 118 live children in 1920, 89.2 in 1930, 75.8 in 1936, and 80 in 1940. With the growing prosperity brought on by the Second World War and the economic boom that followed it, young people married and established households earlier and began to raise larger families than had their predecessors during the Depression. Birth rates rose to 102 per thousand in 1946, 106.2 in 1950, and 118 in 1955. Although economics was probably the most important determinant, it is not the only explanation for the baby boom. The increased value placed on the idea of the family also helps to explain this rise i
A. the baby boom had little influence on the attention of educations
B. before the baby boom, basic academic skill and discipline did not interest educators
C. after the baby, the elder youths still had chance to gain nontraditional, new, and extra services
D. the school system shifted its attention form the lower grades to older youths
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