In the late 1960's, many people in North America turned their attention to environmental problems, and new steel-and-glass skyscrapers were widely criticized. Ecologists pointed out that a cluster of tall buildings in a city often overburdens public transportation and parking lot capacities.
Skyscrapers are also lavish consumers, and wasters, of electric power. In one recent year, the addition of 17 million square feet of skyscraper office space in New York City raised the peak daily demand for electricity by 120, 000 kilowatts —— enough to supply the entire city of Albany, New York, for a day.
Glass-walled skyscrapers can be especially wasteful. The heat loss (or gain) through a wall of half-inch plate glass is more than ten times that through a typical masonry wall filled with insulation board. To lessen the strain on heating and air-conditioning equipment, builders of skyscrapers have begun to use double-glazed panels of glass, and reflective glasses coated with silver or gold mirror films that reduce glare as well as heat gain. However, mirror-walled skyscrapers raise the temperature of the surrounding air and affect neighboring buildings.
Skyscrapers put a severe strain on a city's sanitation facilities, too. If fully occupied, the two World Trade Center towers in New York City would alone generate 2.25 million gallons of raw sewage each year —— as much as a city the size of Stanford, Connecticut, which has a population of more than 109, 000.
摩天大楼还是电能的过度消费者与浪费者。最近的某一年，纽约市摩天写字楼 1，700 万英尺办公面积的增加使电能的最高日需求量提高了120，000 千瓦。这些电能足以供纽约的整个奥尔巴尼市使用一天。
玻璃表面的摩天大楼特别地浪费。 通过半英寸的平板玻璃墙壁损失(或增加)的热量是典型的加入绝缘板的石墙所允许的热量损失(或 增加)的十倍以上。为了减轻取暖设备或空调设备的压力，摩天大楼的建造者们已经开始使用双面上釉的玻璃镶板和涂上了金色或银色反光薄膜的反光玻璃，来减少强光照射和热量的增加;但是，镜面的摩天大楼会提高周围空气的温度并会对附近的建筑物产生影响。
摩天大楼也对城市的卫生设施造成了沉重的压力。单单纽约市的二个世界贸易中心大楼如果完全被占满的话，每年就会产生2，250，000 加仑的污水。这相当于康涅狄格州的斯坦福市这 样大的城市一年所产生的污水量，而康州的斯坦福市拥有109，000 人口。
The preservation of embryos and juveniles is a rate occurrence in the fossil record. The tiny, delicate skeletons are usually scattered by scavengers or destroyed by weathering before they can be fossilized. Ichthyosaurs had a higher chance of being preserved than did terrestrial creatures because, as marine animals, they tended to live in environments less subject to erosion. Still, their fossilization required a suite of factors: a slow rate of decay of soft tissues, little scavenging by other animals, a lack of swift currents and waves to jumble and carry away small bones, and fairly rapid burial. Given these factors, some areas have become a treasury of well-preserved ichthyosaur fossils.
The deposits at Holzmaden, Germany, present an interesting case for analysis. The ichthyosaur remains are found in black, bituminous marine shales deposited about 190 million years ago. Over the years, thousands of specimens of marine reptiles, fish and invertebrates have been recovered from these rocks. The quality of preservation is outstanding, but what is even more impressive is the number of ichthyosaur fossils containing preserved embryos.
Ichthyosaurs with embryos have been reported from 6 different levels of the shale in a small area around Holzmaden, suggesting that a specific site was used by large numbers of ichthyosaurs repeatedly over time. The embryos are quite advanced in their physical development; their paddles, for example, are already well formed. One specimen is even preserved in the birth canal. In addition, the shale contains the remains of many newborns that are between 20 and 30 inches long.
Why are there so many pregnant females and young at Holzmaden when they are so rare elsewhere? The quality of preservation is almost unmatched and quarry operations have been carried out carefully with an awareness of the value of the fossils. But these factors do not account for the interesting question of how there came to be such a concentration of pregnant ichthyosaurs in a particular place very close to their time of giving birth.
在德国获尔兹梅登，那儿的.沉积物给人们提出了一个有趣的分析案例。人们在黑色的、含沥青的海洋页岩中发现了约19，000 年前沉积下来的 鱼龙化石。几年时间内，在这些岩石中取得了数以千计的海洋爬行动物、鱼类以及无脊椎动物的标本。它们的保存质量非常的好，但更令人称奇的是保存下来的育有胚胎的鱼龙化石数目。
在获尔兹梅登附近一个小地区的六个不同的页岩层中分别发现了育有胚胎的鱼龙化石。这表明大量的鱼龙经年累月重复使用一个特定的地点。那些胚胎已经发育得相当完整了。比如，它们的蹼桨已经完全形成了。有一个标本甚至被保存在产道中。而且，那块页岩包含着很多在20 到30 英寸之间的新生幼体的化石。
为什么在其他地方那么稀少的怀孕雌兽和幼体在获尔兹梅登却那么多呢? 因为其保存质量几乎举世无双，采集工作的进行一直是一丝不苟的。大家都认识到这些化石的价值极其珍贵，但这些因素并不能解释这个有 趣的问题：为什么在一个特定的地点会如此集中地出现即将临产的怀孕鱼龙群呢?