Tower BridgeUnderground station Solar Clock, London

A sundial is a device that measures time by the position of the Sun. In common designs such as the horizontal sundial, the sun casts a shadow from its style onto a surface marked with lines indicating the hours of the day. The style is the time-telling edge of the gnomon, often a thin rod or a sharp, straight edge. As the sun moves across the sky, the shadow-edge aligns with different hour-lines. All sundials must be aligned with the axis of the Earth's rotation to tell the correct time. In most designs, the style must point towards true celestial north (not the north magnetic pole or south magnetic pole). That is, the style's horizontal angle must equal the sundial's geographical latitude.

In the horizontal sundial (also called a garden sundial), the plane that receives the shadow is aligned horizontally, rather than being perpendicular to the style as in the equatorial dial. Hence, the line of shadow does not rotate uniformly on the dial face; rather, the hour lines are spaced according to the rule.

where

λ is the sundial's geographical latitude (and the angle the style makes with horizontal),

θ is the angle between a given hour-line and the noon hour-line (which always points towards true North) on the plane, and

t is the number of hours before or after noon.

For example,

the angle θ of the 3pm hour-line would equal the arctangent of sin(λ), since tan(45°) = 1. When λ equals 90° (at the North Pole), the horizontal sundial becomes an equatorial sundial; the style points straight up (vertically), and the horizontal plane is aligned with the equatorial place; the hour-line formula becomes θ = 15° × t, as for an equatorial dial. However, a horizontal sundial is impractical on the Earth's equator, where λ equals 0°, the style would lie flat in the plane and cast no shadow.

The chief advantages of the horizontal sundial are that it is easy to read, and the sun lights the face throughout the year. All the hour-lines intersect at the point where the gnomon's style crosses the horizontal plane. Since the style is aligned with the Earth's rotational axis, the style points true North and its angle with the horizontal equals the sundial's geographical latitude λ. A sundial designed for one latitude can be used in another latitude, provided that the sundial is tilted upwards or downwards by an angle equal to the difference in latitude. For example, a sundial designed for a latitude of 40° can be used at a latitude of 45°, if the sundial plane is tilted upwards by 5°, thus aligning the style with the Earth's rotational axis.

Tower Hill tube station has a large horizontal sundial in a small courtyard outside the Tube station in London, England. 

Sundial, Tower hill station, London

(Taken from wikipedia and other articles)

Kew Garden

The Royal Botanical Gardens, Kew usually called lies on the South bank of the river Thames between Richmond and Kew in 121 hectares in London, England. It is on the Heathrow Airport flight path, so every few minute noisy planes go overhead.

Kew garden's Victoria entrance

 Kew was created in 1759 and the garden celebrated its 250 years 2009 (I was lucky to visit there at that time)

 

It’s the world’s most important botanical gardens. It has a large collection of about 50,000 different plant species as well as many impressive buildings such as the Palm House and the 10 story Pagoda in the 132 ha (326 acres) of garden area.

In 1759 Princess Augusta, mother of King George III, started developing a 3.6 ha large garden. After it was inherited by King George III and he placed Joseph Banks in charge  of enlarging and planting the combined garden. After returning from a journey around the world with Captain Cook Joseph collected various plants from all over the world. In 1841 the Kew Gardens were donated to the state after which green houses were added which includes the famous Palm house and Temperate house. In 2003 Kew Gardens was put on the UNESCO World Heritage list.

GREEN HOUSES

Palm House (1844-1848)

Back view of Palm house

Spiral Stair Inside the Palm house

Designed by Decimus Burton and Richard Turner is a graceful iron structure with magnificent glass. One can find plants from Tropical Rainforest. Walk up the spiral staircase to the footbridge inside the Palm house where the temperature and humidity is high and the view looks good from the top of the tree.

Waterlilly House (1852)

Water lilly house

 It is situated right side of the Palm house. It contains all types of water lilies from to smaller ones. Though it’s not much visited you can find various kinds of plant inside this house.

Temperate House (1859-1899)

Temperate House from Tree Top walkway

Designed by Richard Burton is the largest greenhouse in Kew Gardens. It took 40 years to complete it and was opened in 1899. At that time it was the world’s largest greenhouse.

Prince of Wales Conservatory (1987)

This building has 10 different climatic zones, ranging from desrt on one end to tropical at the other end.

Way to the top

Treetop Walkway

Apart from the Green houses there are other interesting buildings like Pagoda, Queen Charlotte’s cottage, Treetop walkway. Treetop walkway (Xstrata Treetop Walkway) has a wonderful view of some of the greenhouses at the far end while having a feeling of walking midst of the canopy of world of trees. This is a popular attraction at the Kew Gardens which has a platform 18m (59ft) above the ground having a walkway of about 200m (656 ft). This was designed by Marks Barfield Architects.

There are more places to visit like Museum in front of Palm house etc. Underground the Palm house is a marine display though it not much interesting its good to have a look.   

Plant+People museum and the pond with Hercules fountain

Its better if you spend a whole day at Kew. Pack your lunch and enjoy your visit.

For Price, time in and out and other informations click here

London eye

Originally Ferris wheel was designed by George Washington Gale Ferris, Jr., as a landmark for the 1893 World's Columbian Exposition in Chicago. The wheel was intended as a rival to the Eiffel tower (Ht 80 mts). The term Ferris wheel came to be used for all such rides.

London eye (The Merline Entertainments London Eye) is the largest ferris wheel (Ht 135 mts) in Europe. It was erected in December 31 1999. Untill a until it was surpassed by the Star of Nanchang (160 m) in May 2006, and then the Singapore Flyer (165 m) on 11 February 2008.