In this book, the Imam explained the wonders of creation, showing at every stage how all of it is inter related and could not have come into being by chance. In the first session, he explained the creation of man, his organs of perception, the power of his mind, his gradual development. and all the functions of body and mind.
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In the second session. he explained the animal world and its common features; then he divided animals into groups: carnivorous and herbivorous animals; birds and reptiles; and so forth, explaining every group's special characteristics. In the process of doing this he described the donkey. the dog, the elephant, the giraffe, the monkey, domestic mammals, reindeer, the fox, the dolphin, the python the ant, the spider, the chicken, the peacock the pheasant, the flamingo, the sparrow, the owl, the bat, the bee, the locust and fish.

The third session was devoted to geography. geology. astronomy (not astrology) and other related subjects, such as minerals, trees and medicine. 

[Finally] in the last session the Imam dealt with the most common objection made by atheists: If there is a Creator, then why is there so much suffering in the world? The Imam answered this with the same attention to detail as he had shown in the previous sessions, with systematic arguments. This book is a treasure of knowledge, written to refute the ideas of atheists. Everywhere the Imam draws attention to the wisdom and power of the Creator.

[... ]

Below is an interesting excerpt from the booklet:

"Just consider the stars and their distinctive velocities. There are some among them which do not budge from the positions appointed for them. There are others which move from zone to zone and have their distinctive velocities. Each one of them has two velocities - one due to the cosmic motion in the direction of the west, the other its intrinsic velocity in the direction of the east.

This is comparable to the two velocities of an ant on the upper piece of the grindstone. The grindstone moves to the right and the ant in the opposite direction. In such a case the ant will have two velocities - one its own direction, the front direction and the other unintended, along with the grindstone."

توحيد المفضل : قال : قال الصادق عليه السلام : "فكر يا مفضل في النجوم واختلاف مسيرها ، فبعضها لاتفارق مراكزها من الفلك ولا تسير إلا مجتمعة ، وبعضها مطلقة تنتقل في البروج وتفترق في مسيرها ، فكل واحد منها يسير سيرين مختلفين : أحدهما عام مع الفلك نحو المغرب ، والآخر خاص لنفسه نحو المشرق .

كالنملة التي تدور على الرحى ، فالرحى تدور ذات اليمين ، والنملة تدرو ذات الشمال ، و النملة في تلك تتحرك حركتين مختلفين : إحديهما بنفسها فتتوجه أمامهاو الاخرى مستكرهة مع الرحى تجذبها إلى خلفها."

The whole booklet is available from here:
http://www.al-islam.org/tradition-of-mufaddal-pearls-of-wisdom-from-imam-jafar-as-sadiq

Source of most of this article:
http://www.al-islam.org/al-serat/vol-9-no-1-2/scholarly-jihad-imams-95-148-ah-sayyid-saeed-akhtar-rizvi/part-ii