This contribution gives the results of a statistical investigation of 400 extra-galactic nebulae for which Holetschek has determined total visual magnitudes. The list is complete for the brighter nebulae in the northern sky and is representative to 12.5 mag. or fainter. The classification employed is based on the forms of the photographic images. About 3 per cent are irregular, but the remaining nebulae fall into a sequence of type forms characterized by rotational symmetry about dominatin...

The study of nebulae is essentially a photographic problem for cameras of wide angle and reflectors of large focal ratio. The photographic plate presents a definite and permanent record beside which visual observations lose most of their significance. Perhaps the one field left for the older method is the measurement of sharp nuclei deeply enshrouded in nebulosity. New nebulae are now but rarely seen in the sky, although an hour’s exposure made at random with a large reflector has more tha...

Edwin Hubble's work on extra-galactic nebulae revolutionized our understanding of the universe. He meticulously observed these distant celestial objects, leading to the groundbreaking realization that they were not merely part of our Milky Way galaxy but rather independent galaxies themselves. This discovery expanded the known universe dramatically, suggesting that it was far larger and more complex than previously thought. Hubble's observations laid the foundation for modern cosmology, pr...

Edwin Powell Hubble (November 20, 1889 - September 28, 1953), born in Marshfield, MO, was an American astronomer who played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology. Hubble proved that many objects previously thought to be clouds of dust and gas and classified as "nebulae" were actually galaxies beyond the Milky Way. Hubble's name is most widely recognized for the Hubble Space Telescope, which was named in his honor. The following is ...

O Level Physics Practice for structured questions with answers.Good for struggling students of O level Physics who needs in depth look at the mark breakdown in physics questions.Good for self study or returning students.Improve your grades in Physics and get the much needed practice!Multiple Choice and Structured Questions. 2 practice paper in 1 book.

The Easiest Way to Understand Algebra: Algebra Equations with Answers and SolutionsIs your child struggling with Algebra? This beginner-friendly guide offers a fresh, simplified approach to help children grasp the logic behind Algebraic equations. With 90 practice problems, complete answers, and step-by-step solutions, this book makes learning Algebra approachable and confidence-building.Designed specifically for young learners, the tutorial breaks down complex concepts into ...

O Level Physics Practice for structured questions with answers.Good for struggling students of O level Physics who needs in depth look at the mark breakdown in physics questions.Good for self study or returning students.Improve your grades in Physics and get the much needed practice!Multiple Choice and Structured Questions. 2 practice paper in 1 book.

Pierre de Fermat, the famous French Renaissance mathematician who gave us Fermat's Last Theorem, left no mathematical records so far as the English speaking world is concerned. This is because he wrote primarily in Latin. Here for the first time are some of his early works restoring the lost geometry treatise of Apollonius of Perga as well as Fermat's own expansion of plane loci into the third dimension using spheres.This English translation is based on Paul Tannery's 1891 edition ...

Since the first edition of this book was written there has been a good deal of progress in stereoscopy, notably in its commercial and scientific applications; there has also been a number of important developments in connection with the apparatus used for stereoscopic methods and photography. The present edition has been partly re-written and extended to bring it up to date in these respects; no less than 94 pages have been added for this purpose. Whilst amateur stereoscopic photography ha...

This book is intended to be a Fun semi-historical book on the history of Polyhedra, both Platonic and Archimedean as well as special construction methods to make them.This book is of interest to everyone, from the casual reader seeking to understand 3D solids to the serious hobbyist looking for specialized construction methods to build and make Polyhedra from any material including Cartridge paper, corrugated Cardboard, Wood, Fiberglass and even Metal.Polyhedra are excellen...

This book includes my lecture notes for electrical power generation course. The layout, main components, and characteristics of common electrical power generation plants are described with application to various thermal power plants.The book is divided to different learning outcomesCLO 1- Describe the layout of common electrical power generation plants.CLO 2- Describe the main components and characteristics of thermal power plants.CLO1...

"The subject Theory of Machines may be defined as that branch of Engineering-science, which deals with the study of relative motion between the various parts of a machine, and forces which act on them. The knowledge of this subject is very essential for an engineer in designing the various parts of a machine."